Well, I was playing around and there are some weird things afoot:
Tav (Wizard): Always uses Intelligence, be they cleric or wizard scrolls.
Shadowheart: Always uses Wisdom, be they cleric scrolls or wizard scrolls.
Astarion: Always uses Intelligence, be they cleric or wizard scrolls.
Lae'zal: Doesn't use anything, since she has no bonuses, I guess.
So, maybe if you have a 'casting stat', like Shadowheart, it defaults to that, if not it uses Intelligence?
