Hey Hayashi, so problems with the Drow? This area has had me going before, as the archers can get on top of most characters. Prot. from N.Missiles will work for that, and Shield for the Magic Missiles that the Drow cast. Watch out for the phase spiders that appear soon after you spot the bad guys. So...
Search out the area ahead with an invisible character (or try a thief). Once you spring the "trap", have a fighter(-type) positioned front and back of the rest of your party to take care of the spiders. After that, try fireballs and web to eliminate the mages. They'll make collateral damage anyway, so the orc's will suffer. Whilst you eliminate the archers, have your own missile troops disrupt the Drow until you can move into H-T-H and finish them off with the pointy end of your favourite
satirical comment
.
Hope that helps.