Welcome to Chorrol, BretonBlood, have a Fishy St--- err.. I don't think we give fishy sticks here at Chorrol. Have some cake instead.
I gotta say, now that I'm gaming on PC, I'm rather torn. I probably have the power to make vampire NPCs a lot more vulnerable to certain things, especially daylight. They attack us during the day, sometimes. I'm really not a fan of vamps simply walking around in daylight all casual-like, but whatever. I've tolerated it.
In TES4, I use Maskar's Oblivion Overhaul to make vampires take actual sun damage. I figure hey, if the Player Character can take sun damage, why not NPCs? .... Not sure if this would work in Skyrim. I mean, to some extent you gotta figure that TES is not traditional Earth lore. They do things differently in the Tamriel universe. Still though...