That final interaction in the Astral Prism should have been a proper "Dialogue-Boss" like those so prominent in act 2. Make all those reactions and interactions, like to Ansur's death by Baldurans hands and him dominating Belmane, possibly causing her strokes, actually matter. When the player still engages him in a positive, trustful way, there should be the option to remind him of this. The weight of this argument is way more than what a singular Persusasion check can convey. There should be half a dozen checks and saves, from Persusasion, Insight, History to Will saves, simulating not only an argument, but a psychic struggle, between 2 conjoined minds.

As it is, the dialogue has no reactivity and railroads you into one of 2 situation without any regard for how you developed the relationship with him over the game, and that goes against one of the core design elements of this mostly fantastic game.