For Spell Thief I can just get rid of the steal, since I was thinking of how to implement his thief aspect. 

And for Tier 4, it is limited to once per battle and does basically leave him with a scant amount to use just Ghoul Fists, but he can't use more than that until he drains magic to replenish his reserves or rests. On the other hand a clean hit will transfer the opponent's remaining magic to him.

I think it'll be fine though, a lot of his nullification is based around making impact with his own magic, so unlike other forms that just make barriers or straight up cancel spells, I think it'd be while difficult for a straight caster to deal with, isn't impossible if they use their spells wisely, plus more physical fighters will be fine against him.

Anyways, I've made the changes.