He could actually provide an interesting mechanic for these fights. He's got the massively powerful charged attacks that could potentially obliterate a small town, but he's vulnerable the entire time he's charging them, and his only instant use attacks are to summon a water sword, throw his flasks, or bonk them with his staff (not very effective against superhumanly durable demons). The others would have to protect him or risk losing their heaviest hitter. Or heaviest ranged hitter at least...

It would add a better dynamic than just "ok, everyone CHARGE!!". In my opinion at least.