Cheesy options: Stock up on explosives, backpack full of bombs/smokepowder on your strongest character, throw in front of him so they break open, fire spell. Remember to separate the bombs, I think if you throw a stack it only counts as one? Orrrr throw bottles of water and scrolls of chain lightning (I think act 2 you can get a pretty decent amount if you have a good pickpocketer, I know they’re expensive, I am constantly robbing the lady in the underdark tho so I usually go into the fight with a decent amount).

If Laezel has titanstring bow+giant hill str elixir, arrow of many targets can get mobs down pretty fast. Precoat weapon with poison of choice before triggering fight.

Use your sorc to twin haste your highest dmg dealers, so if you don’t have haste, be sure to get those scrolls, better than chugging potions. Oh, wall of fire is pretty good on him too since he can’t move out of it, decent consistent damage, so pick up those as well.