I have a discussion of the build.
Storm Summoning
Gale. KB->KD makes this more practical, but truthfully I think it's a power you should skip if you could. The activation time is too high and the low accuracy Cone nature makes it difficult to use well without spending a lot of spots you'd prefer not to spend.
O2 Boost. Dealer's choice here. The power is useless for you and it's only marginally useful in groups. However, many groups will be annoyed at a Corruptor who can't heal or buff at all.
Snowstorm. The only reason use for this power is to knock enemies from the air. Whether or not that's a worthwhile use is up to you.
Steamy Mist. Take and slot up to reduce endurance and (maybe) increase resist damage.
Freezing Rain. This pairs with Whirlpool in primary and should have the same recharge slotting. Otherwise, a couple of slow will push it near the slow cap.
Hurricane. End reduction primarily. -hit if you've got the slots. KB->KD doesn't seem necessary here due to the way it gets used.
Thunder Clap. Skip. It's slow and only Mag 2.
Tornado. Slot like any other recharge-intensive pet. Here, KB->KD and Force Feedback recharge reduction both seem like solid choices.
Lightning Storm. It's a big AE damage ability; slot it as such.
Water Blast
This is where it gets a bit odd due to the nature of Tidal Power and what it does to your rotation.
In terms of a pure damage rotation, you can do AB, Dehydrate, AB, WJ, WJ, AB, Dehydrate, WJ. This requires 62% AB, 102% Dehydrate, 136% WJ recharge. Note that you get +50% more healing from Dehydrate if you consume Tidal Power with it, so you won't be healing as optimally as you could (Dehydrate is about 50% more healing when it consumes Tidal Power). More realistically, you can also throw HB into the mix and not waste the second tidal power stack. However, taking all those offensive powers means you can't take both supplemental AE (Whirlpool and Geyser are must have). You can theoretically intermix Gale as your 'delaying tactic' and keep enemies on the ground.
The Cone technically does more damage, but Water Burst seems more thematically appropriate and is a lot easier to use/slot.
Ordinarily, I'd skip the Aim-style Tidal Forces. However, it makes a bit difference with Geyser and gives you another way to (intermittently) expand out your rotation to maximize damage with the double-tap Water Jet (Tidal Forces + Whirlpool/Dehydrate consumes a few seconds).
That means 8/9 powers in primary. 7 of them will ultimately be 6-slotted (Tidal Forces only needs triple recharge):
Aqua Bolt. Lean heavy on the recharge here - you need this to be up every other time you activate a power.
Hydro Blast. This can be a more conventional damage slotting since you don't need it to recharge nearly as fast.
Water Burst. I think heavy recharge works here as well since you'll be using it not only as damage but as knockdown.
Whirlpool. You need heavy recharge here to match Freezing Rain.
Tidal Forces. Just recharge.
Dehydrate. Slot this as an enemy target heal rather than a damage effect.
Water Jet. Slot for damage.
Geyser. Slot to reduce the recharge as far as practical, then damage.
Power Pools
I don't see anything particularly necessary here beyond the usuals. Since its an entirely ranged build, Flight seems tempting. However, I don't believe that Hasten is really all that necessary on this build since it lacks many long recharge powers and the basic rotation can only be sped up so far. I like Fire for the Epic.