I always think of Astarion as 1/4 Elf, that's how I'm roleplaying him at least
Astarion is a full blooded High Elf but he's also a 200 year old vampire. When it comes to his character design, I think the developers might of had a difficult time figuring out how to combine his elf and vampire side. From what I see, the only elf features he has is his angular type face, his ears and his body shape. As for his vampire side, the only thing he had are his fangs and red eyes. They could have designed him a little better. If I were designing him, I would change his eyes and make them slightly bigger, a little slanted and bigger pupils. That would make him a little more elvish. I would also change his hair color as he is already pale enough.
Yeah. the red eyes and teeth really give him away for his vampire nature. Fortunatly, vampire traditionnally have hollowed cheeks and hight chiseled cheekbones, which goes well with the elf style; his pales skin and cinder hair does the rest. I think Astarion really does look how he is supposed to look, and I really appreciate his expression too, very realistic for his personnality.
Yes, he behaves very realistically. And I don't think they need to make a lot of changes to his model, just a few adjustments to make his face a little more delicate. The most important thing they need to improve is the eyes, make them bigger and sharper. I think that would make him such an impressive figure.
[edit] Maybe change his eye color to a deeper and shinier red.