Mana Burn is your friend, my man (does damage based on the current size of your mana pool - a hit with that as your 1st move can do over 40 damage if you've got a decent score in the skill). And Greater Ward is even more so (diverts all damage from the next attack into mana - recharges better than Wraith plus you don't take damage).
Mana Burn turns otherwise tediously or even dangerously long fights into easily managed ones simply by knocking off huge chunks of the enemy's HP right off the bat, and Greater Ward means you never need to worry about running out of mana, so long as you don't let yourself run dry - just keep casting it until your pool is full again.
it is a bit ironic that the best spells for combat are not in the Battlemagic school, I'll grant...