One thing Ive been doing is IMBUEing all champions with INT >12 There Int will affect the damage dealt plus (maybe wrong here) it seems to affect the "To Hit" of spells too. My caster with 15 INT does way more damage and seems to hi more often than one I used with INT of 10.
Another thing I do is pile all new casters with my Sov and run around levelling up the group fighting NPC's doing Quests and such (early thru early mid-game) If I get 6+/- casters plu my Sov thats a lot of mana each turn and at 8 and 16 essence they get access to some nice summonings Minor Elementals and Elemental Giants.
Finally, when I can afford it I start equiping my casters (unless they also have fine Str AND Dex AND Con attributes) with bows and keep their mana near max without being maxed and then use the bows as much as possible...works well so far and since the out of memory bug amoung others is preventing me from finishing any game, I will just play until I cannot then begin a new game...sort of feels like I bought a half-baked potato! But I do Look forward to playing through an entire game!
Cheers,
Gene