Try Wall of Moonlight instead.

That fight just begs for multiple Webs, too. If you did some thieving in Kuldahar, you should have two Rings of Free Action, allowing your tanks to run wild among the helpless enemy.
That was a fun fight on HoF.

Entangles, Webs, Slow, WoM, Recitation, Prayer, Curse, about 5 Spike Growths, Fireball, Skull Trap, Sunscorch and Alicorn Lance galore, etc. etc.
DE lvl 3 is harder than it could be because of the lack of access to magical ammunition. You have to take most stuff down with melee weapons or spells.
On the plus side, where else can you hit 20+ enemies with one fireball?
Have you run into the blast skeletons yet?