I don't know how you can say Aerie could sub in for any primary caster.
She gets two level 6 spells at her highest level. A bard is a better caster. Jan Jansen is a better caster by being an illusionist. If you aren't playing a caster you have to plan the game around getting Edwin, Imoen or Nalia.
Also, Minsc has no quests. Korgan at least has one.
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