So I jumped back into this a week or so back playing the turn based mode.
Wizard is pretty overpowered in turn based IMO. Not only can they be the best AOE nukers and pretty good crowd control, but a pure wizard can be just about the best melee tank in the game at high levels in turn based mode.
This is based on the fact that most of the wizard's buffing spells are free actions, letting you buff yourself to godhood on turn 1 and still take an action.
I'm at level 16 right now and if I want to tank I take the following steps:
First make sure you're wearing light armor or robes so you can go asap in the turn order.
Then on turn one, run directly into the enemy and cast:
infuse with vital essence (lvl 2) do this first so that all your subsequent casts get the +5 INT bonus and they last longer.
Then Arcane Veil (lvl 2), Wizards Double (lvl 1), Displaced Image (lvl 3), Ironskin, (lvl 4), Flame Shield (lvl 4), Arcane Reflection (lvl 6), and Piercing Sigil (lvl 8)
These are all free actions. Finally with my turn I can either cast Citzal's Martial Power or go ahead and start attacking.
The only limitation as a tank compared to fighter or paladin is lack of engaged enemies, but you can gain 2 bonus engaged enemies by using the club Kapana Taga and upgrading it, carreid by the pirate Fyrgist (level 15) east of Port Maje. Then you can use a shield for another but I prefer 2 weapons just because my defense is so ridiculous already and I want to do a little more damage.
But the neat (and OP) thing is, I didn't have to sacrifice the ability to nuke everyone with AOE spells with my build. My Wizard is still damn good at that. I can choose whether to be a casting wizard or a tank during any given encounter based on my party and the enemy.
Another great thing is that it's not one of those builds that only works at the end of the game and is a hindrance for the most of the game that you have to string along. You can't use it as a great tank until near the end but until that point it's just a normal wizard, and wizards are great.