[Boron]

Versus fragile enemy mages Rain of Stones and Earthquake might work. Your Dai Oni can cast both of these spells.
You could also use your Hanyas to also cast Falling Fires.
They could do eagle eyes, phönix power and then 3x falling fires, cast spells.
Or skellispam.

Your archers need only few resources, so you can replace them usually faster then the enemy can replace his casualities.
So you only have to win most battles without losing too many mages, the troop losses you can replace faster than your opponent.