Ice/Dark is a great combo that is very versatile and very active in combat. You can cover several roles in combat, often switching roles many times in one battle. I/D is also arguably the best Controlling Corruptor. The level of control can even approach a Dominator, but you will have to work much harder then a Dom to achive similar results.
First, let me give a rundown of the powers and my experience with them.
Single Target attacks: Ice Bolt, Ice Blast, Bitter Ice Blast
I will comment on all together, since they are basically very similar in use. With the three strung together and fully slotted, they will take down a White con minion. The one important thing on this attack chain is to have Ice Bolt be the last in your chain if possible. This is your smallest attack, and should almost always Scourge when it hits vs a White Minion as the last part of the chain. Without that Scourge, the three attacks will NOT take out a White minion. Of course, depending on the target, buffs and debuffs, this may not be the optimal attack chain to achieve Scourges, but in most cases, having your lowest damage attack hit last will significantly improve your overall damage.
One other main feature of the Ice Blasts is that the activations are very fast (about 1 second each). This gives you more time in combat then other sets that have longer activation times. Although not really a down side, the fast activation of the chain and the 12 second recharge on BIB means that you will have a wait between when the chain ends, and when you can start it again. If you want a seemless attack chain, you will need to add Power Pool attacks and/or several Recharges in the powers.
As far as Slotting, I have run 2 Acc and 1 Acc & Tactics with good results. This hits fairly reliably up to +3 to +4s. Damage I believe is an automatic 3 Dam for all of these. For the last 1-2 spots, recharge or End Rd are good choices. The amount of recharges is a bit personal preferance, but the more that you can fit in the better imo. Of course, you will want to find a balance between the added End usage of the quicker attack chain vs maximized damage.
AoE Damage: Frost Breath, Ice Storm & Blizzard
Frost breath I have the least expereince with. I tried it a bit on test, and I was not that impressed. It is a fairly narrow cone, and it takes a few seconds to line up to get more then 1-2 mobs. So, in reality, it is going to be about 4 seconds to use effectivly. In my mind, in that time I can get off a full chain of single target attacks, Fearsome Stare+Twilight Grasp or something else. In my mind, I would only take it if my main concern was to maximize AoE damage or to fill out an attack chain. For the attack chain, I would probably just take Air Superiority instead.
Ice Storm will generally provide more damage then Blizzard thoughout the night. Now, the reason I say this is that even though it does considerably less then Blizzard, with the recharge differences, you will be able to use it approx 6 times as often. The reason I bring this up is that alot of people just see the string of 1s for damage, and assume that IS is not doing that much damage. This just is not true. When slotted for Damage and Accuracy, it will do approx 1/3 of the damage as a BIB. As you can see, if you are hitting 4+ targets, the damage can really add up. Add to this the fact that each tick of damage has a chance to scourge, and it is a very useful damage tool. I/D also has the advantage of Tar Patch to help insure that most all of the ticks actually hit (Along w/ adding damage.)
One question that comes up often is why do -res debuffs not seem to affect damage. The reason is that each tick is rounded to the nearest whole number. The added damage is being applied, it is just that each tick is so small that you normally will not see a difference in each individual tick. Also, until I7 comes out, IS is considered a pet for damage, so many buffs such as Aim will not affect IS. I believe that Assault and Tactics will affect IS, but have been to lazy to actually test it as of yet.
The second feature is that IS will cause a panic in the mobs, and will scatter them. This can be used to your advantage as a minor form of crowd control, as the paniced mobs will have reduced attacks as they flee the area. I have used this many times to buy a few seconds when a second group aggros.
One other use of IS is that since it does not require Line of Sight, then you can use it to pull without recieving an Alpha Strike. Of course, you will have all the aggro from the pulled group, so you need to be very careful if you use this tactic.
The downside, of course, is that IS will gain you lots of aggro from this power. Normally, this makes the best use of this power after a brute or MM has collected some aggro so you will not draw all the fire when the mobs escape the panic area.
As far as slotting, it depends what you are using it for. I believe that 3 Damage and 1 Acc will get you the best damage results. Some will slot slows, but I feel that it is a waste since I/D gets Tar Patch as well.
Blizzard is the last power in the Ice set, and it is a very good Nuke power. Pretty much, alot that was said for IS applies to Blizzard as well. It has great synergy w/ Tar Patch, and really can take down +2 minions w/ ease. I really had fun with this power.
With that said, I did respec out of it. The reason is that although the damage is incredible, the End Drain was very problematic in groups. I had found that I was generally more valuable doing the normal Crowd Control, single target damage and Debuffs then the added damage that Blizzard added. Of course, keeping stock of Catch a Breaths would aleviate that, but I hate having to rely on having a specific inspiration to make a power worthwhile. The other problem was that it didn't really seem to turn the tide of battle as much as just speed up a combat that would have been won anyway.
By no means am I discouraging a person to take Blizzard. It is a very fun and entertaining power. It is especially useful solo. It just did not fit my playstyle.
As far as slotting, 3 Damage and 3 Recharge is probably the best option. Acc is not really needed as Blizzard has a good bonus to hit.
Single Target Holds: Freeze Ray, Bitter Freeze Ray and Petrifying Gaze.
All three of these are very similar. FR and BFR have the same hold time, and both have the Ice block hold graphic. Although it may seem a minor point, having that very visible graphic can be a great help in designated what is held and what is not. The main difference between FR and BFR is that BFR does some damage, but has a very long animation time (3-4 seconds) while FR activates quickly but barely does any damage. PG is very similar to FR with no damage and a less noticable graphic.
Basically, all you really need are 2 holds so that you have the ability to hold bosses. I believe the obvious choice is FR and PG. FR should be your main hold when you only need a single hold for pesky lts because the graphic is so noticable. PG rarely gets used except for bosses, in which case the added magnitude is gold.
As far as slotting, Acc should be similar to your single target attacks, 1-2 Acc. I believe 3 Hold and 1-2 Recharge will give you the best results as far as holding durration vs End/Activation Time used.
AoE Control: Fearsome Stare, Black Hole, Howling Twilight
Fearsome Stare is an incredible power. This power locks down a wide cone shapped area of Mobs with a fear effect. Fear effects basically mean that a mob gets one action for every time it is damaged. The reason I value this higher then many AoE holds is because you can make FS permanent on up to +1-2s with repeated applications. This one power has the potential to turn a near wipe into a cake walk. Also, in addition to the fear effect, FS has a minor Acc debuff so that even when the mobs get an attack, they have a lower chance to hit. Fear can also affect Bosses with only 1 application, unlike most holds.
As far as slotting, 2 Acc, 3 Fear, 1 recharge will let you Perma fear most even cons. 1 Acc, 3 Fear, 2 recharge will let you Perma Hold most +1 - +2 minions.
Black Hole I do not have alot of experience with, only using it on test. From what I have seen, it is actually better then most of the flack it gets. The upside is that it is another AoE that will prevent all damage while it is in effect. It can be a great 'oh crud' power when a second group adds. On the downside, intangible mobs are impossible to hit, and somewhat difficult to seperate from a regular mob (although I though it was not as bad as advertised). The main problem though imo, is that when they come back into phase, you will have all the aggro and recieve an alpha strike from them.
Overall, it can have some use, but I/D has enough control that in most builds BH will not be needed or wanted.
Howling Twilight is actually a Rez, but it can also be used as limited CC. It is an Auto Hit, Mag 2 Disorient in a small radius that lasts about 10 seconds or so. This can be used as an emergency form of crowd control, but, if you do, you will not have the option to rez a fallen teammate if the CC is not enough to save lives. Of all the powers in I/D, this one probably offers the most difficult decisions as to use; Proactive as CC or Reactive as a Rez.
As a rez, it is very good since it Rezs all allies in a small area w/ full HPs and End. On the downside, you need a mob to target, so it is only a incombat rez. Of course, if you have TP foe, you can sometimes pick off a single target for a rez. Recall friend lets you drag the bodies to the next combat and rez them all at once.
As far as slotting, I tend to not have any extra slots to drop into HT. If I did, it would be a choice between recharge and Disorient durration, depending on how you use it most (Occasional CC that you want a long durration, or you want the rez/cc up most every battle)
Buffs: Aim, Shadow Fall
Aim is one of those powers many love, but I just do not feel it is that great for my personal build. It adds +100 Acc and +50% damage for 10 seconds. As far as the damage, that basically adds another 50% to your single target attack chain every 90 seconds. Imo, I would rather take Air Superiority instead to increase damage, as you do have a gap in your attack chain that it would fit, and it will add better sustained dps.
Now, where I may consider taking it again is when I7 comes out and the damage will be added to Ice Storm and Blizzard. That extra 50% could make a big difference in playstyle. Also, for PvP, anything that helps adds quick damage is appreciated.
As far as the Acc, there are not that many powers I need to hit once every 90 seconds. The two that it could come in handy for are Twilights Grasp, and your Holds. As far as TG, I wouldn't reccomend in most situations, because if you Need the heal to hit, you probably do not have time to add the activation time to TGs activation. As far as holds, using this before using two single target holds will almost insure that you will be able to hold a boss within seconds. I haven't had to many issues with the holds hitting as is, but ymmv. Fearsome Stare is also a viable reason to take this, but in the few groups I feel I Need a high percentage of hits, I will just use a few +Acc Insperations. Again, ymmv.
Of course, the +Acc would be very valuable in PvP, so if you plan on PvP, it is a good pick up imo.
For slotting, I would just use recharges. I haven't had enough PvP experience to know if adding +acc would be worthwhile.
Shadowfall is a great power in many subtle ways. First off, it grants you and those around you stealth. Combined with Superspeed, you have complete invisibility. This can be invaluable for setting up Fearsome Stare to get the most mobs in its effect. The combonation also allows you to 'stealth' a mission to the end and finish it w/o going through all the minions.
The second effects of SF are a buff to resistance and defense. The defense buff, like most all defense buffs, is quite small. The Resistance buffs, on the other hand, are fairly decent, somewhere around 18% base, enhanced closer to 30%. This only affects Psionic, Energy and Negative Energy Damage though. Because of that, I would reccomend that you evaluate what kind of damage the mobs are doing before you decide if you should keep it active durring combat or not. The end drain is noticeable durring combat, so I do keep it off as much as possible.
One other thing you should be aware of, is that most NPC hostages will lose sight of you if you have SF active. This can be frustrating to some groups that may not realize this, and keep losing the hostage as they come in range of your SF.
As far as slotting, this is another power I would like to slot more, but do not have the extra slots for. I would reccomend Resistance Slots, and perhaps End Reducers if you are having End problems. In most cases though, using this power only when needed will take care of most End porblems I have found.
Debuffs: Darkest Night, Tar Patch
Darkest Night is a core power to /Dark. It debuffs a Mobs Damage by about 25%, and their Accuracy by about the same. It is an anchor power with a decent sized AoE effect. Being an anchor, you need to be careful where you place it. In most groups, I will pick a low priority Lt, as Bosses tend to be a primary target, and minions die pretty easy. On the other hand, if we are facing a group where the main threat is the boss, I will target him, since I want him under the effects at all times until he dies. In all honesty, at the higher end game, I do not use DN many fights, as my Crowd Control abilities migate enough damage that it is not needed, and I use the extra End for offensive powers. As you progress w/ a group, you will be able to find when it is needed, and on what targets are most likely to survive and stay in the general area to be most effective.
DN often is used as a pulling tool for those combats that you would rather not rush. This can be a good thing, as the Alpha Strike will be lowered, but on the other side, you will aggro everything in the area. This aggro can be used to your advantage is some circumstances though. One tactic involves dropping a DN and running around a corner, while dropping a Tar Patch at the corner. This will tightly group the mobs for AoE attacks such as Ice Storm and Blizzard. It can also be used to maintain aggro on a mob, but keep it alive. I encountered this farming Devoring Earth for the Badge you get when you kill the Buff Crystals. In addition to keeping the low level mobs aggroed on me, incoming damage was reduced to basically nil.
As far as slotting, I believe that 3 to hit Debuffs are essential. 1-2 End Reducers may be in order depending on your End usage.
Tar Patch is the ability that make Ice Storm a viable damage source, among other things. Tar Patch does three things, it reduces run speed and it reduces mob Resistance and it supresses fly. You also do not need LoS to place it, so it can be used as a pulling tool.
The speed factor can be useful in several way. First off, it combines beautifully with Ice Storm and Blizzard, as it will keep the mobs under the effect for a longer time, and therefor maximize the damage both of these powers do. Reduced speed can also be used to keep a melee mob away from you. I have successfully killed Bosses that I should not have been able to just by playing 'keep away' in a tar patch.
The -Resistance is great, as it actually multiplies the total damage your attacks do by about 1.3, and not just the base damage, as a buff to damage would do. Again, this has great synergy with AoEs as Tarpatch has a fairly wide area of effect.
Slotting can go one of two ways. Increased slow will make your Ice Storm and Blizzard more effective, although they both already have a slow component. I believe that you will hit the cap w/ one of those AoEs and 2 slows in Tar, but I have not tested that. The other option, and perhaps more useful is to slot for Recharge, as Tar Patch is so very useful, you would like to have it up every fight. Currenetly I have Tar Patch Slotted w/ 2 Slow and 2 recharge, along w/ Hasten, and I have no problems having it available each combat.
Heals: Twilight's Graps
Some may want to put TG as a debuff, as it does debuff Acc and it stops regen on the mob its used on for a short time. The main use I have used it for is as a heal though. It is a medium AoE heal that radiates from the player, and heals for one of the highest amounts in the game. The two main downsides are that it requires a target to hit, and you must hit the target for the heal to work. Since it requires a to-hit check, try to target minions with it, unless you need the -regen on a Boss/AV. A secondary downside is that it takes about 2 1/2 seconds to fire off, and in that time alot can happen, from a death to an injured party member running out of range. Overall though, it is a very good heal that can patch up breaks in your defense.
As far as the debuff, it does lower Acc a bit. While not steller on its own, it adds to all the other /Dark effects that lower Acc. The more important effect on some Bosses and AVs though, is that it stops/slows their regen. At the speed that some AVs regen, this could be tide turning, and should be applied even when the group does not need healing.
As far as slotting, most go with 2 Acc, 2 Heal and 2 Recharge. I generally do not need to spam heals very often, so I go with 2 Acc, 3 Heal and 1 Recharge. This gives me a large heal that is almost guaranteed to hit (I keep tactics going as well) every 6 seconds. Before I picked up Tactics, I went 3 Acc, 3 Heal. Perhaps a bit excessive, but at the time I was fighting +3-+4s, and when a Heal was needed, it Had to hit.
Pets: Dark Servent (AKA Fluffy)
This is a great addition to your arsenal. DS has 5 Powers that it will use, Chill of the night (An AoE aura with a minor dot and -acc), Twilights Grasp (Identical to players), Petrifing Gaze (Identical to players), Darkest Night (Similar to players, but single Target) and Tenebrous Tentacles (Cone attack w/ an Immobilze. Very useful when combined w/ Ice Storm or Blizzard). Fluffy also has a decent amount of hit points, and can tank fairly well with his -acc debuffs and TG.
Fluffy lasts only a few minutes, but the power should be up again before he expires. (I havent used him w/o hasten, so not sure how long normal recharge is) You can only have one out at a time, and it is fairly mindless. He will follow you and attack any mobs he encounters. I have not seen him TP to my position as a MM pet will, so be mindful when traveling with him if you leave him too far behind that he does not gather aggro for you.
One of the main ways I have found to use Fluffy is as an Alpha Absorber (The power has a decent range to summon him). Plop him in the middle of most groups, and he will survive long enough for you to get a Fearsome Stare or Darkest night off, many times longer. You can also run through a group Invis, and have him aggro the group that way. I have encountered a few times where the aggro was transfered to me while I thought I was still hidden that way, so use caution that. The last way to get Fluffy engaged is to us Recall Friend on him into mobs. I have done this while Invis with SS+SF and did not gain aggro when I used that method.
For slotting, I would recommend 1 Acc and 3 To-Hit debuffs as a minimum. Every power Fluffy has (except one) is a Acc debuff, so that will maximize his effectiveness. As far as other slotting, heals are useful as he will spam TG fairly often.
Playstyle:
Although there are several way to play and I/D, I feel that the set is primarly foccused on Damage Mitgation and Single Target Damage. The Damage Mitgation comes from three sources: Crowd Control, Acc Debuffs and Heals.
Crowd Control I feel is the first and best form of defense of an I/D. A fully slotted Fearsome Stare will literally let you tackle any amount of minions/Lts that can fit in the cone. Since it can be permaed, as long as you have endurance, you can keep a group locked, and fight them one at a time until they are all dead.
In a group of 10 Mobs, you will probably lock about 8 or so. That means you have reduced incoming damage by 80%, no other debuff can come close to that. This is why I put Fearsome Stare as my first option for Damage Mitgation. FS will be a bit less useful if people are throwing lots of DoTs around, but it will still reduce mob damage output by a large degree. And, the way I feel on a team, if someone wished to wake up a feared mob, they are the ones taking the aggro from me, and they have to deal with the consequenses
And, unlike Sleep, the mob will go back under Fear after it gets it's one attack/action.
Locking a Boss w/ the two holds may or may not be the best thing you can do. Keeping a Boss locked will take alot of your Time and End, and reduce other contributions to the group you could be making. Unless it is a very nasty boss, dropping Fluffy near it (For the -acc aura) and putting a DN on the Boss may be a better use of your time. Other Bosses, such as a Succubus, it is well worth your time to keep them on Ice till they are dead. I will usually throw a DN on them as well, so that the DN can have an effect on the rest of the combat while I concentrate on the Boss.
The next line of defense is your -Acc debuffs. DN stacked with Fluffys Aura will greatly reduce incoming damage and status effects. Add to that the -Acc of Fearsome stare and TG, and this adds another great layer of protection.
The last line (besides HT's Rez) of defense is your heals. Although not a 'healer', an I/D can heal very well, and TG is used to patch any holes in your CC/Debuff defense. There may be times that you need to 'spam' TG in a very tough encounter, but even then, you will still have 6-8 seconds between each TG to use other powers, so you are never just a heal-bot.
As far as the damage aspect, I tend to put that in a secondary role to damage mitgation, but even then, Ice is so quick that you can ususally fire off your chain when it is up. The high single target damage has one very important aspect in this build: low aoe aggro. You will already be gaining plenty of aggro from your Fear/Debuffs that by being able to focus damage on a single target, you will reduce the posibilty of a faceplant. This is important, since often a team will need your CC/Heals/Rez to succeed. This by no means is to say that you shouldn't use Ice Storm and other AoEs, just be aware that you need to be careful of return fire from it, and you are much more important to your team alive then dead, even if your AoE can take down 1/2 the spawn.
Another role that I have found to be well suited for and I/D is puller, or perhaps Rusher is more appropriate. In almost all groups I am in, I am the one that initiates combat.
There are two main ways I commonly useto initiate combat. The first and most common is to line up my target while invis w/ SF+SS and open with FS. This will reduce the Alpha strike to almost nothing. I will follow up with Tar Patch and Darkest Night. By the time the group hits the Spawn, most of the mobs are Feared, -Acc, -Res and -Dam, and I will have taken perhaps a few hits from those FS missed. If FS misses more then a few, then just throw in a TG to recover any HPs.
The second most common technique I use is when a group contrains Bosses or Lts that I feel I can not risk FS missing. (Ancestrial Sprirts are one lt that is immune to fear) In that case, I will summon Fluffy into the middle, and either drop DN or FS depending on the mobs.
There are other options, such as using Tar Patch around a corner, or pulling w/ DN, but these two I have felt are the most successful.
Power Pools:
Concealment:
I havent dipped into this pool, and honestly see little reason to since SF gives you stealth, and SF+SS gives full invisibility.
Fighting:
Another pool that adds little to an I/D. Perhaps a dip into it for attacks to fill your attack chain, but I would suggest Air Supperiority first.
Fitness:
A must I would say. Even w/ 3 slotted Stamina I still need some End Reducers to not be constantly OOE.
Flight:
I do not have this on my I/D, but as stated before, AS can be a very good power to help fill out an attack chain if you are looking to be more offensive.
Leadership:
I think that this build is fairly slot heavy, so if you can fit in Tactics to lower your Acc enhancements, I would suggest it. Tactics is also very good for PvP. Of course, on the downside, w/o any status protection, Tactics getting knocked off gets annoying.
Leaping:
I do not have this, and I want to work it into my build when the cap reaches 50 strictly for Acrobatics. The only inspiration I try to keep on me are Breakfress, since lack of status protection is the biggest leading reason for deaths on an I/D imo.
Medicine:
No real need for it unless you wish Stimulent.
Presense:
No real need. The fear effects are okay, but vastly inferior to FS.
Speed:
Hasten and the stealth from Superspeed made this my choice of travel powers. Both abilities work very well with an I/D, but as mentioned above, there can be made a strong arguement to Leaping instead. I do not see the need/end available for whirlwhind in most circumstances.
Teleportation:
Recall is great for Fluffy and dead bodies for Rezes. TP Foe can be useful for pulling around corners and to grab a doner for HT. If I had to pick one, Recall is more valuable in most cases for an I/D though imo. Telportation can also be used toTP to the other side of a spawn to drag Fluffy through it.
Okay, I will most likely edit this in the future to correct the many mistakes I am sure I made somewhere in this guide
I hope that this has been helpful for newer players, and more experienced one, let me know what I got wrong
Considering electric/electric doesn't benefit from permadom nearly as much as the other combinations, I don't understand why people are so fixated on "PERMADOM OR YOU'RE USELESS!" especially for a set that only effects like what? 2-3 powers?