There's a bit of a pattern in Act III with the companions becoming less "people" and more "video game characters" - collections of pixels we're not really supposed to get attached to or take seriously. Possibly just another symptom of Larian running out of time to polish things.
Couldn't have put it better myself. Honestly, entire act 3 is just a mess. The only thing that is polished in act 3 is House of Hope.
Halsin turns into an atrocity, we get an obligatory brothel orgy scene (using companions with backstories least suited for it), Mizora is forced on you and does nothing apart from standing there propositioning you for sex, your companions don't care whatever you do with Haarlep, and the game ends with an abuse victim running away in pain while the rest of the party make fun of him.
Don't get me started on how pointless Mizora is. I can't even get her to leave! Once I'd exhausted all of her conversation options, I asked her to leave cause at that point, she's there to ask you for sex and then just...exist in that space. She doesn't even become an ally for the ending so she's literally there for no other reason.
But getting back to the point of the thread, Astarion's ending points to a larger issue with the whole of Act 3. Like a lot of people have said, the tone is entirely different from quest to quest.
Astarion's companion quests was one of the most unique experiences I've had in a game. Never have I felt such genuine interest and concern for a video game character.
Couple that with like...hunting down the murderer in Lower City or getting the stupid mail for the post office? Like...the quests are not the same. And the mail and murderer quest last a lot longer than Astarion's quest with very little substance.
It speaks to Act 3 just being where everyone's leftover ideas drained to. They needed a lot to happen so any weird idea that was shouted out was crammed into it to make the Act longer. Definitely done by a different set of writers than the people doing the companion stories.
And Astarion's god-awful dock scene capitalizes on and confirms this.
