Reading through all of this, I'm happy I wasn't the only one upset about it.
I'm hooked at how complex a character Astarion is. Every time I talk to him, I'm analyzing if he's actually being honest with me.
When it's apparent is when he thanks you after you save him from having to bite the drow in Act 2.
To know all of this about it him makes me inclined to tread carefully when it comes to intimacy for him. I want him to choose and want it every time. And I want him to know I really and truly care for him.
It seems so obvious that Larian would want that for the character too. But, based on what we seem to have no choice about (pulling him out of the foursome, having the option to tell Astarion that you would never ask him to be a part of the Halsin polyamory, not being able to run after him when he's burning in the sun, not being able to ask his feelings on any of these instances etc.), Larian doesn't want it?
So was his story arc created by someone independent to the whole overarching story process or something? Because if you were taking into consideration what your characters would want in any given situation, we wouldn't have so many damn tone-deaf moments.