Astarion is absolutely correct in his behavior towards Tav in this case.
The game establishes that you lose yourself once you become an illithid, you're no longer the person your LI knew. It's another reason why he has no qualms to end things with Tav who decided to go for it. He doesn't delude himself believing things are still mostly the same like other companions do. When I watched the vid I was laughing together with Astarion.
He also makes fun of Tav during the epilogue party calling their transformation a travesty, lol. I don't know, I just really like his laughter, especially when he's being a dick. XD One of my favourite ones is when he doesn't know about the ritual and interrogates Petras and Dalyria and trashes them for trusting Cazador. (2:27)
Originally Posted by Marielle
I once really liked the video in which Astarion leaves Tav if she encourages him to bite Oblodra.
He also has a very good reaction if you tell the spawn who try to abduct him that they can take him. He might actually have the most possible scenes where he breaks up with Tav.
