I fought Zehir with 1 stack of orange cats, and for the final battle, I used a dwarven army. I also leveled up Wulfsten in Single Adventure mode, but I didn't like it. It seems like there are 2 schools of magic, but there's nothing to cast in the last mission from either of them; mass curse and teleport would have been much better. There weren't any problems in the battle itself, but it just wasn't comfortable. The strength of mass stone and dodge from the dwarven set depends on the light skill. So, I prefer leveling up a combatant with light.
By the way, instead of summoning, I gave him defense, because the Academy's troops are not very durable, so at least they will take less damage.