@Raze: I know, but that's not the point. I'm not looking for a way to keep Bairdotr in the party, I'm criticising what I think is a bad design decision. Now don't get me wrong - in other RPG's NPCs would leave the party, too, like in BG2, but there it was clear why (differences in alignment) and the player got some advance warning, whereas Bairdotr's defection comes out of the blue.
@Felixg91: I think I'll just start over with a new party, just realized my fighter is built badly. If this fight is so much harder than it's supposed to be, others will be the same. I didn't even know there were stat books you could buy, so I only got the stat raises from regular level ups. Along with the sub-optimal skilling, this has resulted in me hitting a wall here.
Anyway thanks for the help guys, I really appreciate it!