It turns out the trick to that fight is figuring out a good alpha strike. It's tough because you can't get close without triggering a dialogue that either starts the fight immediately, or causes her to leave the room to go start the raid on the druids. So what I did was toss a bag of gunpowder I got from the Zhentarim right next to her table, to start the fight. Then Gale shot it with a firebolt and blew her the fuck up, for like half her HP.
Honestly the most annoying part of that fight is the sheer number of nearby goblins, even if you destroy the bridge. There are like three snipers that come over from another room if you start fighting.
For the hobgoblin, I got him to follow my main character up into the rafters, then knocked him down, and the rest of my party nuked him while he was prone. I was hoping the fall damage would just kill him outright, but alas, it wasn't enough.
Also, it turns out the best way to move an enemy that you absolutely need to move is the illithid powers. They don't have a chance of failure, they just always knock 'em back, it's great.
Got down into the underdark and tore through the minotaurs and the duergar ambush. The latter gave me a ton of trouble the first time, because, well, I got ambushed, but this time I came from the myconid side and had Glut along, and I did the ambushing.
