In most,if not all, vampire lore, when a vampire feeds, he/she gets "better" in all aspects of it's life. So can someone tell me, in your opinion, why, in TES games, does a vampire actually get "weaker" after it feeds? I feel this very odd.

http://www.uesp.net/wiki/Lore:Manifesto_Cyrodiil_Vampyrum Pay particular attention to "On Our Dual Patrons" and "On Our Conduct" While their supernatural powers are depleted, they appear more human, which allows them to pass as human. That's useful. For some reason, it was carried over to TESV as well.