Update:
The problem was fixed when I started a new game. I was using a mod to play on impassable terrain, worldedit 2.0, and a mod that regenerates the map, so maybe something got lost in translation. In any case, I can't seem to duplicate the behavior.

I also played around with the vampire source code a bit to create a custom clan, but I don't see what I could have changed to fix the problem. In any case, the problem's fixed. It's a mystery.

wait, so these guys can sleep? Ive not seen my vampire get tired ever, none of them.

Yeah. They're suppose to sleep. When the sun goes down they get tired and pass out if you let them. It was a mod compatibility issue for me. I don't remember which one, unfortunately.

Edit:
So yeah. That's the expected behavior. I only knew because I've played the mod before.

i cant even get my vampires to have vitae, it keeps switching to blood and they have no powers. known mod conflicts?