Drain Psyche can work as a replacement for Stamina in build which are not too endurance heavy. Since you're running Leadership toggles and Arctic Air, you'll probably still need Stamina.
It's not the Immobilise itself but the Knockback/down resistance that usuall comes with those powers that counteracts with powers like Ice Slick. I believe Subdue has no knockback resistance portion, so it should work fine with Ice Slick. As for whether or not it's worth taking, well the damage is good. And you can stack it with Chillblain which can help with AVs. It's not a must-have, but it's not a bad power.
Shiver's cone is HUUUUUUGE, which is why I like it. The -recharge and slow components are booth really large debuffs, much larger than Arctic Air (thoguh it doesn't have AA's other effects obbviously). If you like to PvP, it's well worth it.
Do do DO slot tactics. 3 To-Hit Buff SOs, 1 Endred SO usually works. Its endurance cost (which is much higher than Assault, I'm sure you've noticed) means it's worth slotting to get the most out of it.
Well this is my current build atm
1 - ice block
1 - psi dart
2 - Mental Blast
4 - Frostbite (probs later respec to chillblain)
6 - AA
8 - Hasten
10 - Mental Blast
12 - Ice slick (FTW)
14 - SS
16 - Psy scream
18 - Asault
20 - Drain Psyche (will soon 6 slot with 2 acc 2 rch 2 endmod, should hopefully help me with my end issues if i dont take stam)
22 - Tactics
24 - Hurdle/Shiver
26 - Glacier
28 - Subdue/Health?/Swift
30 - Stamina/Vengeance
32 - Jack Frost
35 - not sure yet, will see whether or not i take stam.
38 - PSW (cant wait!)
41 - Powersink (with this and DS could i then spec out of stamina?)
44 - Charged Armour (never heard a good thing about the aoes)
47 - Mu Guardian (heal bot)
49 - Somehthing or other
I mostly wanna stay in melee range though to open will be using ice slick and then jumping in and firing off DS). Atm its mostly for PvE but chances are ile venture into the pvp zones at some point for the fun of it.
I know everyones playstyles vary greatly and no two ppl will likely agree, but thats kind of the point, i wanna read your experiences and then make up my own mind.
Thanks all.
Heya there Mime, you might remember me as Undine from the game, and if I understand correctly, you have the same goal for team-support as Undine does.
Undine sitting at 41 at the moment, I share some general useful information that you might not know. 
Chillbain/Frostbite, I myself have Chillblain, for dropping out flier one-by-one, but Frostbite can keep stuff inside Arctic Air and range of PSW.
Chillblain: easy to use on single targets, works on AV/Heroes, can replace your Mental Blast, is a godsend against robots until you get Jack.
Frostbite: as mentioned above, it can keep enemies inside your powers' radiuses. Obviously not to be used on an Ice Slick, but that's 2+2 and you know it's 4.
Arctic Air is a great, great, great power! You'll find more and more uses to it when you add more slots into it, and it's THE power for pretty much CONSTANT lockdown! Slow, fear effect, confuse, not to mention that it acts like a targeting circle for your PSW! (when you get it, that is)
I have mine slotted with 3 confuses, 2 endredux, and 1 slow, but I run Stamina with my build, so I can live without having the 3rd endredux there. The slow is in there to cap the mobs' speed cap, well, almost. 88.5% or so. Works for me.
Psychic Scream I have in my build, and slotted too, but I hardly find myself using it. Once I got PSW slotted, I didn't bother positioning myself for it's narrow cone, plus, I am more useful being in the middle of things, with Arctic Air and PSW both acting like a debuff. 
Assault/Tactics are great powers in force-multiplying, even the small bonus from Dominators can affect the team's killing ability.
Glacier rocks! While you're in the middle of things, and you see your Domination button blinking, it's a very dramatic hold, and has a large radius. Very. Large. Slot it with your preference of hold duration, recharge and accuracy. Generally having 2 accuracies means that it's not gonna miss half of the bunch against a group of +1s.
Subdue is worth its experience points you have invested so far to get this. There is an 80% chance of immobilization, which can hold lieutenants. The immobilization does not disable Knockback, Knockdown or Knockup. It's a great damage move, take it, slot it, love it.
Jack Frost has gotten a lot more angry since I10, and you don't need the old pantyhose tricks to get him into melee, say, via Recall Friend. He's suicidal at times, but he does a lot of damage and can hold his own with lieutenants. His moves are:
Ice Bolt (I refer this as snowball), he throws it once before he enters melee combat.
Freezing Touch, his opening move. A hold that does respectable damage, but in DoT.
Ice Sword, his weakest melee attack, but still good.
Greater Ice Sword, omgwthbbqhax, this does even more damage than PSW while you're in Domination. Go Jack! 
PSW is just awesome. 'Nuff said.
Patrons I can't help too much with, but if I had a time machine, I'd go back in time and choose Mako instead of Ghost Widow, which I now regret. The reason to take Mu pool is to take Power Sink, a good shield and the most useful pet out of the PPPs. If you plan on going Staminaless, Mu is the choice.
Why I would switch to Mako now:
Waterspout has a long Disorient when it hits, it will help with our slight inability to take alpha strikes if the Brute is feeling a bit cowardish, not to mention that you can slot Stun IOs in it to get some recharge bonus.
And Shark Skin looks just cool, along with nice cold resist for fighting those ice-chucking CoT and against players who just seem to love Ice Blast.
I just got my domi up to lvl 23 last night and he is now fully slotted with SOs and im really really starting to love playing him. Ice slick is an awesome power and -rching stuff to hell is always fun. But I seem to be reading conflicting reports about things and just wanted to ask a few questions.
With DP is it really possible to go staminaless? atm im running assault and tactics, and also usually AA now, and along with DP and firing domination to recover my end, atm im not having huge troubles less im on really small teams. Is it possible or is it better to get it at some point?
Subdue, is it worth getting? its an immob which kinda counteracs iceslick (i took frostbite but only ever use it as a psudo hold and to knock down fliers, but will probs resec to the single target immob later). If its worth getting the slotting it with 1acc 3dam as usual?
Does AA need 6 slots? was going to go with 3endrdx 3 slow as the whole confuse part isnt as important to me, esp on bigger teams ive found.
Shiver, some say its great, others say its nice but not hugely needed. I mostly get into melee range now due to iceslick/AA and DS and then i can use mindprobe happily. Is shiver just good for the lower lvls and then respec out later? It seems like it would be a good opener to go along with scream, but otherwise AA should do the trick.
Also is it worth sloting tactics at all? I know you can stick LotG in there for perma-dom, but for now should i just stick a endrdx in there or a tohitbuff?
All help and advice greatly welcomed.
Domination FTW!