There's no point of fighting the bulette really, even with glut rez it's annoying to navigate terrain. Minimal XP for effort and crap loot. Just run from combat each time.
Minotaurs are easy though. Spectator is much more dangerous in honor mode. Make sure to hit a petrified drow with a ranged attack to spawn it and avoid the surprise round from the cutscene. Keep your team spread out. That's the only dangerous encounter in the underdark really. Grym can be killed by keeping a player up above and chucking down random objects for bludgeoning fall damage, bring lots of heavy things.
I've been pumping the quests in 9 kings. These fuckers are hard as shit