on my caster group i got SK, sham, mage, mage, ench, bst. I didn't even reallly plan on this but was just kinda of the classes i had sitting around. Yeah i think anything over 2 mages is a bit too much, however, mages unlike some other classes seem to have a bit of multiplicative effect for themselves, in that the more pets you have the more dps you do and youll have more mage synergies, but i would not go over 2 of any class either, unless it was just for the luls or i was realy obsessed with a particular class. Necro synergy is pretty nice. If i was patient enough i would consider rerolling a necro for a mage though it also depends on what maybe you want the group for, it might be better to have another caster like a mage over a necro if you wanted to keep the kill rate faster.