Trust me. I did all possible quests and sub-quests.
I even did a musical chair of sorts and did all the NPCs' quests. It's just that I took too long to get Imoen, so there were too few quests left when we exited the Underdark.
Here's a
link of the girls' last few fights to the final showdown.
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If not a Sorcerer, then a Paladin.