[Adept]

Thunder Strikes, Shadow Blasts, Pillars of Fire, Falling Frost, Falling fires.

Those are the artillery I tend to use. Even a few mages can make a difference with those. Arrow Fend is important as well.

I just saw a fellow player of mine really spam thunder strikes and Pillars of fire with Lvl 2 air and fire (indies too, illusionists and fire lords) by having them first cast booster spells and then go at it. Half a dozen Pillars of fire and 4 Thunder Strikes can really mess up the opposing army's day.