Seriously. I purposely closed out Act I without even interacting with him in the first place. I played dozens of hours throughout the beta, and was so sick of his bullshit by the release date. Fuck Astarion.
I'd encourage you to treat him like a PTSD victim that has been a prisoner for 200 years. He is a complex character and he can be good. In my playthough I never really interacted with him besides his questline and you learn a lot about him with Cazador and all that stuff.
I ended up >!stabbing him after he went too far w/ sucking my blood. Figured I would revive him afterwards, but found out I couldn't.!< I didn't like him enough to reload the save.