Since Wyll and Shadowheart were revised, Astarion’s writing is the only one I have a problem with.
IMO, it’s pretty dumb that Astarion always puts a knife to your throat, no matter how many companions you have with you. Unless you are role playing a pacifist, there is really no good reason not to arrack him (in self defense) during either the initial encounter or when he tries to bite you. I don’t mind the writing for Astarion after that, but it’s not surprising that people who are more concerned with role-playing just kill him during one of those two early events.
Counterpoint: denying Gale to join while roleplaying a good character just doesn't work for me. It's really annoying. Astarion gives you a good reason to say "fuck off" multiple times.
Companions doing nothing while Astarion attacks you really sets the tone for later problems, though. Can't switch characters in conversation, apparently. Could have written those scenes better.