I don't think it's a strong argument for us to tell the writer his characters are not ... in character. I'm not bothered by someone like SH making an exception for someone she finds personally attractive.

If (considerable *if*) Astarion's romance isn't meant to be uncomfortable when combined with Halsin's, that could use work. The romance triggers altogether can use work. Even a simple combined fix of better epilogues and getting to go with Halsin would improve the experience a lot. This is about as far as I can stretch my expectations, along with maybe a few more scenes.