Thanks for the thoughtful write up Zeru, I largely agree with most of what's being said there.
I think Lamaros, what's being said there regarding Astarion, isn't that change in his character is bad writing, it's that the approval system i.e. playerreputation is a bad way of implementing relationships with characters, Astarion is a bad dude, but you can game the system to make him like your selfless pc, because...you said the right things to him or decided to kick a baby in front of him, once. I would also say that it isn't impossible to make a compelling narrative around Astarion like this but it requires you doing a lot of the narrative work yourself, but that could also just because of how little we've gotten so far.
Niara, I'm not sure everybody feels so certainly about the malleability of sexuality, not that it isn't the case but it doesn't strike me as being a settled matter.
Garrus is my choice for strong friendship in a game, but maybe that's just me.