From what I know, their regeneration is probably significant enough to counter the sunlight damage, whatever it is. It should probably be disabled in sunlight. They should have to make fort saves vs level drain, reflex saves vs slow, and will save vs fear in my opinion, once per turn (minute), so each different class of vampire is at threat of some kind of debuff. On top of this, they should also be flagged not to run outside, so the only way this can happen is if an MPC leads them to their doom.
Seems like less of a minor issue and more like a major inconsistency to me.