Need help with cold caster

Hi, I've always wanted to make a cold caster , aiming to perma freeze my foes, and now I just started one, however i'm not sure how to make it end-game worthy.

I have many doubts but at least I wanna knwo which skills should I choose. I guess i'll go for spell crit multiplier/chance nods, as well as power charges. Also my idea is to exploit all AOE nods (+ increased aoe gem) on the cleaning skill.

Cleaning - I LOVE Ice nova , but i fear it might be too weak for high level mapping. Currently (lvl 20s) glacial cascade seems to kill much faster, but considering i'm gonna exploit ice damage , i'm not sure if GCs overall damage is going to be that much higher than ice nova endgame?. I really like ice nova circular shape and huge area better but not sure if worth it.

Bossing - Not sure which would have highest dps for "single target" or bossing. Freezing pulse strenght when next to target? ice spear high crit chance? glacial cascade + conc effect multi-hits? arctich breath nice base damage?.

Also, I was wondering if concentrated effect increases freezing pulse/arctic breath damage, since they are AoE but no change on dps is displayed on tooltip.

Any help is appreciated, thank you.

Ice Nova is pretty good, works well end game too. I am playing non crit but if you invest in critting I bet you can easily double my dps sitting at 8.5k currently. For single target I use Glacial Cascade.
Freezing pulse isn't AoE, wont benefit from CE (look at the gem tags). Arctic Breath will.