[Debaser]

If you're reffering to the fight with Tor-Gal (or whatever his name is), it can be kind of a tough one because he has a sick regeneration rate...what you want to maybe do is slowly inch into the room, not quite revealing Tor-Gal but luring the other two trolls towards you. this way you can finish them off and it will consequently easier to finish of Tor-Gal by himself.
you shouldn't have much trouble smashing him with your fighters, considering your PC, Korgan, and Minsc are all pure class warriors. have anomen cast protective magic (defensive harmony, chant, bless on them) and just let them go apeshit on Tor-Gal. maybe having a mage throw a lower resistance (i don't know if its even completely necessary) and then bombard with acid arrows and what not. the trick is to smash him beyond the threshold of his regeneration....good luck