After posting that I hit 50, several people asked me for my build and a guide. Here's a little of that for those interested.
Here is my build for AquaStorm. I dont remember what levels I took each slot or power, but you can just use a progression that works for your situation at your current level. I will try and include notes with any unusual slotting. My only critical suggestion is that you take Hurricane at lvl 12, and Stamina at lvl 20.
I changed my power selection and slotting many times over the course of my career. I used 5 or 6 respecs!!! At various points in my career, I opened up a game-changing power, and completely revised my tactical strategy. Sometimes, it seemed better to respec. In addition, various changes in game-play were brought about by the different Issues of CoH, necessitating changes. Remember that Issue 7 is coming out soon, and it will bring about some changes to Hurricane (nerfing it a bit I heard) and maybe other powers or effects (like knockback and damage boosts affecting pseudo-pets).
Also, please remember that my build is just one of many. I developed it around my playstyle. You will have to do the same. If you just follow my build, you might end up with a toon who cant do what you want him to do. At the same time, if you follow my build, I dont think you will end up with a gimped defender either.
The biggest problem with my build is, interestingly enough, the nerf of Hover that took place with ED. My strategy usually revolved around using Hurricane to rapidly debuff foes while pushing them into a tight clump. With Hover limited to 3 Fly enhancements, I am just not fast enough to do this as safely or effectively anymore. Basically, since ED, AquaStorm has been hurt in effectiveness. I tried using Fly, but the control is just not tight enough. Many times I just use Sprint, but this is problematic if there are obstacles on the floor or if the target is in the air or near an edge.
I recommend getting some tool for pulling. A critical strategy is learning how to pull a group of mobs around a corner so they arrive clumped up, facing a Lightning Storm, Freezing Rain, Hurricane, Voltaic Sentinel, Ball Lightning, and sometimes Tornado. I used to use Zapp a lot, and it is a good option. It will pull anything, except for a sniper. I settled on Teleport Foe in the end however. It allows me to bring a sniper right to me. It works without needing line of sight. It allows me to tp foes right into a corner where they are held in place by my Hurricane. It allows me to tp dangerous mezzers out of their group and right into a corner, held in place helplessly by my hurricane and tornado. The only problem is that it cannot tp bosses, but usually, if Ive pulled out of that group the problem mezzers and snipers and sappers, etc., the boss is no problem for me. If I can tag a boss with hurricane, especially into a corner, hes toast. I could easily handle red bosses this way, although my damage output made it slow work (unless they were alone, and then I could just place everything on them, including tornado, and he would be chewed up quickly).
Recall Friend I chose just because it fit the theme/backstory of AquaStorm (i.e. the idea of rescuing people at sea). Its not necessary for a storm defender.
Voltaic Sentinel used to be awesome because it did BLASTER level charged bolt damage. In Issue 7, they are fixing that bug, reducing it defender level damage, but I still think its a great choice for a storm defender. The reason is because as a storm defender, you will often be moving throughout the combat. Much of our effectiveness is due to tactical positioning, so we are constantly moving around, tagging people with Hurricane, pushing and containing. As a result, we dont have as much time to just stand there and blast. The beauty of a storm/electric build is that it provides several fire-and-forget damage producers who can maintain/increase your dps while you move around doing your debuffing work: voltaic sentinel, lightning storm, and tornado.
Tesla Cage is a critical power to pick, since your most dangerous foes are mezzers. The trick is to mez them first, or debuff them with your hurricane if you cant. Get it and slot it up.
Why did I get Teleport if I already have Fly? Because Teleport is an awesome self-positioning tool, and storm defending is all about positioning, both for yourself, your teammates and your enemies. With Teleport, I can pop into any part of the battlefield where my Hurricane is needed, without either taking time to fly there, or without the risk of knocking back enemies along the way who I dont want to knockback. Its also great for Lightning Storm ping-pong: create a L. Storm on one side of a mob, then tp to the other side with your Hurricane on. They get pinned between your hurricane and your L. Storm! Its funny. Works better if there are walls on either side of them, like in a passageway.
O2 Boosts slotting was purely a matter of AquaStorms theme/backstory. Some stormies skip it, but I dont recommend that. It is very useful even with the default slot, both for a quick little heal (unslotted) or to protect someone from sapping or to wake up someone. If you dont slot it, I recommend just putting an end. red. in it, because it eats up around 15 endurance per use. But if you slot it up, it also makes a quite effective single-target heal, fast and helpful. I have used it many times to rescue teammates in trouble.
Why the Electric Ancillary Power Pool? That was a tough choice. I tried them all on Test. Let me explain. Dark didnt fit my theme. In addition, it didnt fit my playstyle, requiring me to be closely surrounded by a group of foes, which was not how I played (i.e. hurricane!). Power is a good choice, but Power Boost didnt last long enough for my taste, and I dont like relying on clickies. Conserve Power was the most appealing to me, since storm defending is the most endurance hungry defender, but again, I didnt like having 3 minutes (or whatever) when I couldnt use my powers fully while it was down. I would rather put end red enhancements in my powers and use them all the time the same way. Also, Temp. Invulnerability is the worst armor.
I used the Psionic pool for a while, and I think its great! I still recommend that as the top pick if you intend on doing much PvP. The main reason is Dominate. Its a fast, long-lasting, cheap hold. Combined with Tesla Cage, I could hold bosses right away! (or 2 lieuts) This was a god-send in PvE. In PvP, its a beautiful thing. You can shut down a Force Bubble, take out two squishies, etc. Another good reason to take this pool is Mass Hypnosis. While the group is asleep, you can put down SnowStorm without waking any up! The armor is also awesome because it gives psionic resistance. With it up, along with Steamy Mist, you can get 40-50% damage resistance to almost everything!
I ended up respecing into the Electric pool. Why? For a few reasons. Electric Fence is an immobilize which gives knockback on the target. This is the only knockback power available to a storm/electric. Why is this helpful? Because, if you put a Fence on a foe, then drop a tornado on him, the tornado does not blow him away. And if the tornado stays on him, it will chew him up fairly quickly, especially if combined with Freezing Rain. This became a favorite boss killer for me, esp. out in the open. Inside, its not so important, because you can push a boss into a corner and hold him there for the tornado.
Charged Armor gives me even more resistance to energy in addition to that from Steamy Mist, giving me around 80% resistance to energy! Very sweet. (Although Im not sure what the defender cap on resistance is, so this might be lowered by the cap.)
And finally, Power Sink was the endurance helper Id been looking for. With two End Mods in it, I can refill my bar from 2 enemies. It auto-hits, and recharges quite rapidly. Even with hurricane up, I can dash next to two enemies and fire it off. Even thought the hurricane pushes the mobs back, it is enough time for the Power Sink to work.
Endurance is the biggest issue for a storm defender. We run many end-hungry toggles, and we have many end-hungry powers (i.e. Voltaic Sentinel, Lightning Storm, O2, Ball Lightning, Tornado, Freezing Rain, etc.). If you want to cut loose with your full stormy awe-inspiring might (and isnt that why you made a storm defender?), you need some way to reduce endurance costs and increase endurance restoration. The across-the-board endurance cost reductions in issue 6 (?) made our lives a bit easier, but they were canceled out by making Stamina only 3 slottable with ED. Believe it or not, I have come to love the much-maligned Vigilance. I think it makes a very helpful difference for a defender, especially a storm defender.
Make sure to take Stamina at 20, and three slot it. Put End Red enhancements in pretty much every power, esp the end-hungry ones. Consider putting 2 End Red enhancements in each toggle (although Hover doesnt need it since its cheap), but make sure to put at least one in each toggle (again, Hover doesnt really need it). You dont need any in Fly unless you plan on using it a lot in combat, but with Suppression, Fly isnt that useful in combat any more.
Gale is not necessary. Just a matter of your preference. I picked it as my level 49 power. With so many positioning powers, its usually redundant, but occasionally its useful. If you get it, make sure to put 2 accuracy enhancements in it, because its naturally less accurate, and its very irritating when you are depending on it to push back a crowd into a corner, but it leaves 2 foes untouched.
Before ED, another viable build path for a storm/electric was to focus on endurance draining. But with Short Circuit limited to 3 End Mods, and Hasten unable to be permanent, and the recent changes to bosses and lieuts to increase their endurance pool, I dont think thats a very effective strategy anymore. Although, if you want to go that route, you pretty much HAVE to go with the Electric APP for Power Sinks end draining capability or the Power APP for PowerBU. Unfortunately, that means that an end draining build wont begin to mature will lvl 47 or lvl 41 at the earliest! Thats kind of a little late in the game in my opinion, although it might be a fun respec build for the end of your career. Still, this strategy doesnt work well if you have Hurricane up all the time, as I do.
Why no Thunderous Blast, you may ask? I had it at one point, and its a lot of fun. Unfortunately, its not that useful to a storm build. Heres why. First, after ED, it is limited to 3 damage enhancements. Thats still not too bad, especially after Aim + PowerBU, but its more of a finisher, not an opener. The other, even more important reason, is that it completely drains your endurance and makes you unable to recharge endurance for 10 seconds. This could easily get you and your team wiped out, because you are depending on so many toggles!!! As soon as you use it, all these shut down: Snow Storm, Steamy Mist, Hurricane, Hover, and Charged Armor. Basically, all your personal and team defenses. I decided I was more valuable to a team with all my toggles running than I was with a low-powered nuke. Still, its a viable option, and certainly a cool power. I still think I might respec into it again some day instead of Gale.
Why no Aim? I had it at one point for a while. I just didnt find it very useful. I dont rely on big AoE attacks or snipes. Tesla/TP Foe were the only reasons I could see getting it, but I was accurate enough with those. Still, if you go with Power BU, Aim might be a good supplement. If you get Thunderous Blast, then definitely consider Aim. In addition, a HUGE change that is reportedly coming in Issue 7 is that Aim and Power BU will boost the damage of Lightning Storm and Voltaic Sentinel and Tornado!!! This alone makes me encourage you to consider taking Aim at some point in your career if this change indeed happens in Issue 7.
Why no Hasten? I used to have it, when it used to be able to be permanent. Now it cannot be, and just like with Conserve Power, I dont like relying on a clicky which means that half the time I am not as effective as the other half of the time. I like being able to produce a steady output of offense and defense, unaffected by a buff timer. But you might like it. Its still a viable option. Just be careful if you get it not to let your endurance drop down below 20 when Hasten is up. When the timer ends, you lose 20 endurance, which could drop some or all of your toggles. (Another irritation with it.)
Why no Thunder Clap? I used to have it, when it was auto-hit. I learned it was quite useful in certain situations, even with Hurricane up! I could descend down on the enemy from above. At a certain hight, the Thunder Clap would affect them, but the Hurricane had not yet pushed them. But now, with Thunder Clap being unreliable, needing at least 2 accuracy enhancements, and me having Hurricane up all the time, I found that I hardly ever used it, so I respecced out of it. A Storm/Dark defender might still love it when combined with Dark Pit, but for me, I couldnt justify it anymore in my tight build. I was sad to lose it however, because it just looks so darned cool.
Ive probably forgotten some things, but feel free to ask. In the meantime, heres the build:
O2 Boost: 3 x Heal, 1 x End Red, 2 x Rech Red
SnowStorm: 2 x End Red, 2 x Slow
Steamy Mist: 2 x End Red, 3 x Dam Res
Freezing Rain: 3 x Rech Red, 1 x Slow, 1 x End Red, 1 x Def Debuff
Hurricane: 2 x End Red, 3 x ToHit Debuff
Tornado: 1 x End Red, 3 x Rech Red, 2 x Dam
(note: 3 Rech Reds allows me to bring up a new tornado just as the old one dies out. If you only use Tornado occasionally, you dont need this. There are several ways to use Tornado, so slot according to your use of it.)
Lightning Storm: 3 x Dam, 1 x End Red, 2 x Rech Red
(note: 2 Rech Reds allow me to bring up a storm just as the old one dies out.)
Gale: 2 x Acc
Charged Bolt: 1 x Acc, 3 x Dam, Range
(note: CB comes with a default range of 70. Lightning Bolt has a default range of 80. I got sick and tired of needing to move closer to hit with CB when LB was in range, so I added this Range enhancement. Allows me to use CB and LB without moving.)
Lightning Bolt: 1 x Acc, 3 x Dam, 2 x Rech Red
(note: added 2 Rech Reds to increase my dps, esp against bosses. Yes, I took my second blast power, and Im glad I did! Sometimes, I just have to disagree with TMS, but I still love her!)
Ball Lightning: 1 x Acc, 3 x Dam, 1 x End Red
Tesla Cage: Acc, 3 x Hold, 2 x Range
(note: one Acc and 3 Holds is minimum to make Tesla effective. Beyond that, you might want to put in 2 Rech Reds to bring it up more often. I decided on increasing Range because many times my powers would blow a critical foe beyond the default range of Tesla, but I didnt want to move closer to the target because I was holding an even more dangerous foe in a corner with Hurricane, and I didnt want to free him. With more range, I could keep the one foe in the corner, and hold the ranged foe, without moving.)
Voltaic Sentinel: 3 x Dam, 2 x End Red, 1 x Rech Red
(note: VS doesnt need an Acc enhancement. It rarely misses. You used to be able to have up more than one at at time, but no longer, so only one Rech Red is needed. The 2 End Reds are important because this is an expensive power to activate.)
Hover: 3 x Fly
Fly: 3 x Fly
Swift: 1 x Run
Health: 1 x Heal
Stamina: 3 x End Mod
TP Foe: 1 x Acc, 1 x Rech Red
TP: 1 x End Red
Recall Friend: 1 x Rech Red
Electric Fence: 1 x Acc
Charged Armor: 2 x End Rech, 3 x Dam Res
Power Sink: 2 x End Mod
There ya go! I hope you have lots of fun with your stormy! Let me know how it goes.
Sincerely,
AquaStorm, another mighty Storm Defender on Virtue
Wow! This really gives me a lot to think about. I have been considering respec for my stormie/elec so that i could pick up tp self/foe. I love the knockback, and it is true...sometimes tanks/scrappers dont appreciate it. 
. I try to be sensitive.
It was hard to pass up on being able to blast foes off their feet with a mighty wind.