I re-rolled the ending many times (I made a quicksave during the braincrash cinematic), and only once did Astarion speak and then it wasn't to me but to Minthara, because it's completely random and your relationships, what quests you've done, what characters you've developed, may no role in who you hear from. I heard from Minsc, who while I recruit was literally never in my party, in most of those rolls than from characters who were in my party the whole time. Laz was the only character to have an actual scene. And I assume thats only because I did Orpheus ending, not anything to do with her.
