Shar-Teel's strength is that she can be incredibly versatile. She can work as a damage dealer (but not as a tank), and her high Dex and Str allows her to be a pretty good ranged fighter (especially in evil playthroughs where you won't take Coran, for example), and also Dual into a Thief and become a ridiculous backstabbing machine. I basically beat the toughest bosses in the game by backstabbing with Shar.
She's no good for tanking, and an evil party has Kagain for that job anyway. Now Dorn with even better strength and okay con takes Shar-Teel's role as damage dealer. It's a perfect combination to have her as archer or just throwing daggers (before she can get proficient with bows). Plus, due to dualing her, you'll have a thief who can wear helms.
Comments
hopefully the planned evil Thief is one of those two.