I've encountered 2 solutions: 1) put spellcasters (with plenty of Battlefield
Dispels) on the other side and 2) limit magical "enhancements" to units to no
more than one for offense and one for defense. If you let them stack, you'll
soon have the priests and wizards laying down spells that make a unit nigh
indestructable (try bless with bark skin other along with some combat-
enhancing stuff and you'll soon have a unit of knights with a melee and
defense of 9!!!) With such an over-powered unit, I've seen entire battles
decided solely on the attacks of that one unit.

I've also limited how fast a spellcaster can learn new battle spells down to
one spell level (and a research action) per month. After all, coming up with
a battle spell is often a group effort (spellcaster plus assistants) and there
must be myriad combinations to try before just the right solution presents

- -DKE