For example if you buy the artist in Zhentarim hideout - there is an option to tell Astarion that he is your slave, and he approves of it.He also both approves if the MC tortures Liam or gets tortured by the follower of Loviatar; is it just because he is a vampire, or is there some loose screws in that porcelain head?
There are definitely some missing dialogue chains with Astarion; possibly just not triggering completely.
The most obvious one is if he kills you MC during feeding, I mean... Really? He doesn't address this at all?
I've been retrying different quest paths to see, if I can meet the Hunter to get the knowledge that there is a vampire lurking about. Basically confront Astarion and tell him I know or that I am suspicious of him?
I tried both letting Astarion kill the Hunter and leaving him alone, without the knowledge on my PC that Astarion is a
the vampire;
For reference and
and flipping out.
I don't think Astarion kills him just because he feels like we are being pulled in by a story of this mild hunter.
This dialogue pops up if you tell him 'What the hells? He could have helped us!'
Another thing is that if you tell Astarion after killing Gandrel out of nowhere - 'Trust you? After that?' - he responds with
this.
If my point isn't clear yet: I believe Astarion is seducing the PC to be obedient and not to question him. He wants a full trust from you, but sees why you wouldn't and I had the same feeling through multiple playthroughs.
Is he already on the power hunt as soon as he joins the party? He might have even thought he could just control us all, at some point; if the tadpole grows strong enough.
In datamined VA I found him saying: 'Never play a player.' and 'Oh you never know, someday you might end up as me?' Neither if which did I recognize from my previous playthroughs. Lastly I believe he will likely say this at some point during your encounter in Moonrise:
'Trading some whelp we've just met for impossible power? It's a fine deal.'
Unfortunately I went through several different paths, there wasn't a new dialogue option for when he would eventually trigger the feeding scene and reveal he is a vampire himself, nor was there any new dialogue option when we found the dead boar.
Only after the cinematic you can go to him and ask
this, if you already killed the Gur; but he doesn't reveal anything new and sticks to his story. When we didn't kill the Gur before Astarion's reveal, there was no new dialogue.
There is also a way to get the knowledge that it is Astarion that the Gur is looking for before he tells you he is a vampire -
for reference.
If you hire him after, you can't address this at all.
You might be right that Astarion identified Gur based on appearance; I tought he looked bit too much like a generic human tbh