Since he is out of business the fastest - everyone is aiming at him - I can forget all the fancy AOE spells I equipped him with.
That's the problem. You dont equip Gale with AoE spells. You prepare CC spells, counterspell and buffs. Counterspell shuts down enemy caster until you can properly cc him with banishment, polymorph or any other option that works. And Shield + Mirror Image allows gale to tank the first turns.