The first is that while Astarion's characterization is solid and kinda interesting, the more it goes, the more it feels like they're not making a companion, they're making an antagonist.
I think it’s interesting to speculate how Larian might have ended up here. I wonder if it’s the origin problem - from a single player perspective having a companion like Astarion feels crappy but it might be not where such ideas originated.
In the very first BG3 Gameplay reveal Astarion was used as a playable character. I could swear feeding on Shadowheart and killing her was part of the show, but I can’t locate the moment so maybe I am getting things mixed out.
Either way loosing control as Astarion or feeding/being fed on by a coop player are different experiences - especially the latter would be more likely to be laughed off as a funny moment between the players, rather then worrying about in game characters and how would they react. And if that’s the reason behind him being as he is, I am somewhat fine with it as long as a decent number of other companions work decently as companions. I have been not recruiting or killing him during feeding scene for the last couple patches, and I think Astarion would need to change very substantially for me to not do that.