Those Duergar guys are not so tough - they have one weakness; when the warriors attack someone, they don't switch targets unless you somehow disappear.
I usually have Imoen with Stoneskin running around while Minsc and Jaheira kick their running butt.
Mages are annoying and the best way to defeat them is to have someone with high HiS and MS attack them with bow and then HiS as soon as they start casting a spell, so that their spell is cancelled. It takes some time though.
[ 05-23-2004, 10:36 AM: Message edited by: Leslie ]