The problem I have is this. If I kite him too slowly around the room the slimes he summons do too much damage to me before I can kill them. If I go too quickly the entire room fills with gas. Either way I die far too fast despite some > 7kish armor, 850-900ish resists, and 50-55k life. My DPS certainly leaves much to be desired at 15kish and that's part of the problem, but then fixing that problem would be extremely expensive and blizz hydra kiting just isn't as fun as my barb so this character's a much lower priority gear wise.
So my questions:
If I were to switch it up and go for some 20-25% crit chance which I can do with gear I already have would that be enough to critical mass diamond skin spam tank him down?
If I went for (some attack skill) is 17 AP on crit enough to be able to spam it?
Do Wizards have some lol easy button to this fight like Barbs that I'm just missing?
You definitely want more crit with the critical mass build but you don't necessarily need to try to face tank him. You can slowly kite him around and chunk him every time he spawns his minions or walks to the edge of a cloud. I was able to do it with ~20k dps but I imagine if you don't optimize your damage well it might be difficult to kill him before the enrage timer.
I recently had my fit with Ghom. I don't want to tell you how many times I tried, and how much gold I spent on repairs, cause then everybody would know bad I suck. I switched up a few skills for this build: Blizz/snowbound, Hydra/venom, Magic missle/seeker, Energy armor/prismatic, Magic weapon/Force weapon, Diamond skin/enduring skin. Passives were Glass Cannon/Arcane Dynamo/Galvanizing Ward. I had 36k damage, 6k armor, 8-900 resist all, no extra crit, 46k life, and 250 LoH.
The absolute key, no matter what build you use, is kiting him slow enough so that the room will start clearing out when you come back around. I watched some videos that showed people killing him just going around once, but I didn't have enough DPS to do that. With 15k DPS I know you won't either. I had to use every square inch of the room to slow him down and the Templar helped with his charge a few times also. You will need to keep Ghom on the outside so that you can pop in the center if you have to. I watched a few videos of people using teleport, but it caused the gas to spread out when I tried it.
Watch some videos on YouTube, it helped me just to see people actually beating him. I had him down to less than a 1/4 health so many times and I would get so mad. It is possible, but I would get more DPS because that will help you get him down faster so that when you mess up a little and the gas is on each side of you........well, that would be the time to hit Diamond skin.
It's closer to 16k but yeah, pretty bad. It would get a fair bit better if I used some of the crit gear I had laying around but not sure if blizz/hydra even can crit.
Exactly how much crit would I need to tank it with diamond skin and/or freezelock him?
17 AP on crit is near perfect for two items. Barring finding some amazing Wizard hat I really couldn't do better... but that wouldn't be enough for the standard Energy Twister/Explosive Blast/Frost Nova setup?
And 50k damage? Lol, I have a third that with an 850 dps weapon and meh source. That's far more crit gear than I have or am willing to get.
You don't need 50k damage. I easily did him with 20k damage when I first started critical mass build. Now I'm up to 36k with critical mass. 50k is a joke.
As for tanking him, you might get away with 17 ap-on-crit if you have 40% or more crit chance. 25% you simply will not be able to do it. Unless you're willing to completely re-gear, you need to abandon any notion of respecing critical mass for the fight. Just blizz/hydra him.