To maximize AA's effectiveness, you need to max slot for Confuse. To allow your character to do anything else, you need to maximize EndRdx. Nothing else really helps the power be more effective, so if you can do that AND add some damage procs, that's good slotting. I have the two Confuse damage Procs and was able to keep max Confuse and EndRdx. I don't have my build handy at the moment, but you should be able to figure that out in Mids. I think it is a combo of EndRdx/Confuse and Confuse from the purple set, one more EndRdx/Confuse from Malaise, a common EndRdx and the two confuse procs, from Malaise and Cacaphony.
Accuracy, as far as I know, does nothing in the power. As an Ice/Storm, you have other slow options, so Slow doesn't help that much. Currently, the Contageous Confusion proc will confuse your pet, so that's not ideal -- but that's supposed to be fixed with I-15.
There is a lot of debate about Freezing Rain. Some folks slot it for Recharge, and then as many procs as you can fit. I have 5 of the Lady Gray Defense Debuff set, plus a common Recharge, but that may be taking the defense Debuff farther than it needs to be. Still, the set bonuses are nice.
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On my 50 Ice/Storm, I have AA slotted:
Malaise: End/Confuse
Coercive: End/Confuse
Perplex: End/Confuse
3 damage procs
Gives me 85% end redux and confuse while maintaining 3 procs. You could ED cap both w/just 2 procs, of course.
I'm not sold on procs for FR--I merely have it 3-slotted w/Lady Grey's (all 3 containing the word "Recharge"). It's not ED capped for anything, but it recharges in 20sec which is what I wanted. My build is ultra tight (high def) so I basically wanted to make sure FR was up as often as I needed and skimped the other aspects of the power, though I still get 48% def debuff & end redux out of my slotting. If you're not specializing, FR should be 6-slotted, maximizing rech first.
Tho the OP didn't specify, Steamy Mist is tricky too, esp if you're looking to maximize its damage mitigation. I went 3 LotG (+rech, Def, D/End) and 3 Aegis (Res, Res/End, R/E/Rech).
An Offensive Guide to Ice Melee
For Freezing Rain, I went with 2 Undermined Defenses, 3 Lady Grey (including proc), and one other proc (either the KB set one or Positrons.) Look to max recharge, with high end reduction, and some defense debuff.
I'm running an Ice/Rad, but thought I would chip in my AA slotting...
At 41 I have:
<ul type="square">[*]Malaise Illusions End/Conf and the Proc (Set bonus of 2.5% Recovery)[*]Cacophony End/Conf and the Proc (Set bonus of 1% Recovery)[*]Impeded Swiftness Proc[*]Generic IO Endurance Reduction[/list]
I also run Choking Cloud, Assault, Maneuvers and Tactics and am IO'd heavily for +Recovery and +Recharge so the 2 piece bonuses fit right in with my plan.
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Long time player of an Ice/Storm, and here's my current slotting for a lvl50 Arctic Air (5 slots):
Malaise's Illusions: EndRdx/Confusion and Chance for Psi Damage
Coercive Persuasion: Confusion/EndRdx
Perplex: EndRdx/Confusion
Cacophony: Chance for Energy Damage
For Freezing Rain, I went with 6 slots of:
Achilles' Heel: Chance for Damage Resistance
Undermined Defenses: Defense Debuff/Recharge; Defense Debuff/Recharge/EndRdx; Recharge/EndRdx; Recharge
Touch of the Lady Grey: Change for Negative Energy Damage
The point of this slotting was maximum recharge. FR is pretty debuffing on it's own so trying to make it available as often as possible was my intent. Also, the procs are fun to have for a rain power that is cast every fight.
Main Character: Ice/Storm/Ice Controller (Justice, 1340 badges)
I see a lot of ppl slotting FR w/the Achilles proc. Does that actually work out? I mean, that's really only *really* useful for hard targets--sure, it's nice if it procs on a bunch of minions or lts, but those are going down fast enough anyway w/FR up, so really, you're using it for bosses and higher. It's gonna have a chance to fire once every 10 sec, right? And its duration is 10.3 sec, so basically, it's a 20% chance of being on at any time, which works out to a 4% total debuff. FR itself is a 30% -res debuff, so you're using a slot to get a 13.3% return, which doesn't seem like the best use of a slot, esp in a tight build.
As a counterexample, on my Kat/Regen, I have the Achilles slotted in Gambler's Cut, which cycles a around 3~4x per every 10 seconds in my attack chain, which means the odds of it being active during a given 10 sec period is around to 50~60%, so basically a 10~12% debuff on average which is very much worth a slot.
An Offensive Guide to Ice Melee
Thanks all for the suggestions..Currently working on getting the third damage proc but for the moment I've got malaise's proc, the proc from cacophony, Malaise's end/confuse, perplex's end/confuse, cacophany's as well and until I get third damage proc a Confuse/Range proc from malaise (out of cheapness) and its already working like a dream..Once again thanks all for the suggestions.
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I see a lot of ppl slotting FR w/the Achilles proc. Does that actually work out?
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Mine really isn't that tight of a build. Looking it over, I don't see where I'd toss the extra slot. Maybe in O2 Boost (right now it only has the default slot). Otherwise, I'm happy with it.
To me, this is really an "invisible" proc; you never really see it happen, but you know it's firing from time to time. 
Main Character: Ice/Storm/Ice Controller (Justice, 1340 badges)
I slotted AA with 4 procs:
3 confuse procs including the purple
1 slow dam proc
the remaining slots go to the end/conf IOs from the purple and malaise set.
Steamy mist provides confuse resistance, so at least for ice/storm I haven't run into any issues with Jack turning on me.
I overloaded FR with damage procs too, I think I have 1 level 50 Recharge reduction in the power and the rest procs including the achellies heel.
Another power you may consider slotting for procs is frostbite. You can fit 3 in there and spamming it in conjuction with FR and AA will get you pretty decent return on the speed of arrest.
Going this route will mean you need extra recovery though. Numinas and perf shifter and miracle procs help tons here, but it's going to be more costly.
Hello all, so after taking yet another several month hiatus I came back to check out CoH and as always roll up another controller..My current project is my Ice/Storm controller who I have fallen in love with but as I'm getting higher with him and moving towards IO sets several powers confuse me on what to slot them with..The two biggest powers I have trouble thinking of how to slot with IO's is Arctic Air and Freezing Rain..In terms of AA I'm not sure if I should be slotting it with a slow set or a confuse set, which set from the two, or which IO's to use for them..For example all the confuse sets have Acc IOs should I be putting those into AA just for the bonuses? At the moment no where near being able to afford purples with him but will be running several taskforces in the coming days so I can afford almost any other set..Any help is much obliged.