Can you imagine how much cooler it would be if the first time we saw him, he was spider climbing down a wall head first? Or into a room on the ceiling? Or misting in at night down a tree or something. Instead he's just kinda bouncing in place in the middle of the road.
Personally if they're going to do a vampire, we should meet him after he's just drained Aradin and still hovering over the body. Maybe we trap him by the river where it's rushing water and then he makes a plea where the PC can either bind him using some kind of artifact we get from our skeleton pal, or destroy him with weapon we get from our skeleton pal. And if we choose the later, he shouldn't just die but explode into a puddle of ooze or something. Do it proper vampire that way, and I'm in. If the party comes upon him, and they don't have any stakes or silver weapons or holy water, or some equipment to manage vampires, then Astarion should TPK the party and fade to black with him eating the MC. That would be entertaining at least. His personality is a bit ridiculous, but I think they could do more in the set up that might make it better.
