I never managed to finish bg2 my party couldn't do the multiple rounds of combat at the end of tob without resting my main was a ranger that couldn't really do anything to the boss because iirc you needed +6's to actually hit at all. and I think I had +5s bow/arrows. pretty sure most of my dudes were level 30 but I just couldn't make it through that much combat without a spell reset even spamming spell breach and using alsorts of things to push it.
suffice to say I enjoyed bg2 I didn't like the mind flayer portion of the game that much, It seemed like they would be a prominent part of bg3 I just remember going through the areas with them was a save/load fest. random one shots from mind blast. I'm sure you could do something to prevent your dudes getting one tapped by them but its been a while since I went through it. I have the extended from gog so I really should try and actually finish it one day. its just a long game going through amn and then into tob.