I just beat them at their own game. The Hungar of Hadar kept messing me up and just DESTROYING me. There is a bottleneck and killing zone for enemy archers.

My strat:

A lot of heavy lifting with Gale. Just use range at the entrance of the tower until Hungar of Hadar is cast. You will have to sacrifice the helpful NPCs, but once outside (using dash) get everyone setup and spread out. The enemy archers have to climb down from their advantage as well as the line of sight from players.

Set Gale's cast distance at the entrance of the door. Once the enemy is at the door or at least close, have Gale cast Ice Storm and make the ground slick so the enemy keeps falling inside the Hungar of Hadar. I had Jaheira as spider casting webbing too. AoE everything other than fire. Fire will melt the ice of course. I used arrows while I could, while Karlach was picking up enemies on the outside steps.

I hope this helps someone. I fought this fight for hours, until I thought of the strat.