Does lots of cheap mages spamming skeletons help with the banning? Also, I suppose you could dilute the small archers with bandits/indys to reduce the effectiveness of the banishment there. You'd still need some shock troops... maybe summons?
Anyway, I have trouble playing on the medium maps with just 4 normal AI's... too often, they overrun me before I can establish a defense
So I'll sure get a rough treatment in human MP