ice. May as well stack up those slow and recharge debuffs, plus you get powerboost. I could see psi being good as well for debuffing recharge with ice primary, but its lower damage which puts many people off.
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Id dont think there is a particular synergy, although ice and psi would stack -recharges.
Personally, I dont find psi low damage at all, except for psi dart which is only useful for domination building (which it does very nicely IMO).
Ice/Thorn is a nice combination with the slows from ice and thorns does decent damage with aim 
thePhilosopher Martial Arts/Regen/Fire Scrapper
theRegulator Empathy/Energy/Soul Defender
Total Inertia Ice Blast/Kinetics/Psy Corruptor
Total Inferno Ice Blast/Thermal/Leviathan Corruptor
Lol Phil, that you or your bro posting? 
I've seen him pwn enough heroes to know the power of thorns
thePhilosopher Martial Arts/Regen/Fire Scrapper
theRegulator Empathy/Energy/Soul Defender
Total Inertia Ice Blast/Kinetics/Psy Corruptor
Total Inferno Ice Blast/Thermal/Leviathan Corruptor
its not just the torns damage, aim is a godsend and the -def numbers in thorns are insane, start a chain and you miss next to nothing
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That is true, even a well slotted SR is in trouble when you start the attack chain with Aim, + let the -defense do the rest, its like having Forge or Fortitude levels of hitting them, totally negates their defenses, and allows you to hit with those nasty nasty slows.
@Rooks
"You should come inside the box... Then you'll know what I mean."
Ice/Ice is great in my opinion...love it to bits...up to lvl28 so far and going well.
/Thorns is reeeeaaally nice. Chuck in Poisonous Ray for even more -def and a really nice -Res debuff for more damage 
.
My Plant/Thorns has %chance Build Up and a whole bunch of +damage procs and buffs from sets too .
I played with an amazing Ice/Psi' Dom' on Union last night. The build looks an amazing amount of fun play . I'm totally sold on rolling one.
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I played with an amazing Ice/Psi' Dom' on Union last night. The build looks an amazing amount of fun play . I'm totally sold on rolling one.
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Oh, I think Ice/Psi should really be tons of fun. A friend of mine has built one after seeing my Mind/Psi as living proof that /Psi is not low damage (unless the enemy has high resistance which is seldom enough). If anything it's a late bloomer, but you can't tell me with a straight face that spamming Psychic Shockwave in the middle of an enemy spawn (powered by an infinite amount of endurance due to Drain Psyche) is low damage and Ice/ should have the right tools to keep enemies inside Shockwave range.
If it has eyes, you can blind it, if it has blood, you can make it bleed, if it has a mouth, you can make it scream.
Well I play my Plants/Thorn in a wild rampage and like to be right in the middle of spawns and the carnage . Plant has amazing control. Anything not confused or held is easily tanked by 'Creepers, and everything charges fast enough to spam it all out just about every mob 
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Creepers to tank the alphas, confuse, AOE immob', hold anything stray, Fling Thorns, scream and charge in hell for leather - rawr!
The Ice/Psi' Dom' played a lot the same way, so that's me sold .
Sounds completely normal to me.
You will have fun.
If it has eyes, you can blind it, if it has blood, you can make it bleed, if it has a mouth, you can make it scream.
Ok, i have decided to go for ice/ because it has some really nice powers in the set but i'm wondering what to choose for my secondary power so if you could give me any advice id be really grateful
Thanks in advance