So anyone who likes sunshine how are you planning to combat the vampires?
my plans:
use the Agent of Strife on any vampire bosses to eliminate the health drain, and ice form to stop them transforming, vamperic weapons are a must, mercer fray's sword of devouring would work well. invest in paralytic poisons and staggers to eliminate them at range, they appear to move fast.

I plan on making a pact with Clavicus Vile.

Pretty sure no one's thought of that before. What could go wrong?

You can wack them with your sword.

make sure your horse and companion are between you and them, and use crossbow?

Me + SilverSword = Death to Vampires. Quite good plan XD