I ran into a problem/weird behavior with the 'Irenicus in Spellhold' fight: Irenicus spends an entire round casting his 'Summon Clones' spell, during which he is unprotected and easily killed (= forced to teleport away) by the party. If he does so, the summoned clones don't turn hostile.
EDIT: In fact, after some time the summoned clones are then placed under the control of the party.
EDIT2: Correction: the clones are immobile and green-circled upon being summoned, and after saving and loading become party-controlled.
At any rate, the usual workaround of not interrupting mages before their prebuffs addresses this problem also, so it's probably not worth fixing. It seems that Jon's casting animation is interrupted by taking damage, which is why the lack of prebuffs firing instantaneously is more noticeable in this battle.