So, the .14a update tweaked some things with vampires, and that's cool. The -100 opinion hit could definitely make things more challenging for a ruler. Unless, of course, vampirism spread like a rampant STD and damned near every single noble in the gameworld has been turned into a bloodsucker within a century and a half. Which is precisely what's going on in my current game.
It seems that even with the big -100 opinion malus, the AI considers vampirism too damned good to pass up. And resisting the urge to become a bloodsucker is really expensive. (Thanks to my character's wife being turned, he was having to pay 80-90 gold every few minutes to have a healer cast Cure Disease on his mysterious neck-bumps.) Of course, that's actually really cool and makes a lot of sense; of course vampirism would spread like wildfire among the nobility of Tamriel. However, some way to stem the tide would be interesting and appreciated.
One quick-and-easy fix might be to add a "Expel Vampires" intrigue option, like the "Expel Jewry" button added in Sons of Abraham. If that's too brute-force, though, maybe some sort of event chain where you gather non-turned allies and set up some sort of vamp-extermination plot? Like, "let's get a bunch of them to gather at this castle, and then we'll burn it down around them." The plot has a % chance of working, and causes some of said castle's improvements to be destroyed, but a bunch of vampires are dealt with. (And maybe the successful plotters get a "Vampire Slayer" attribute that gives an opinion bonus to non-vampire characters and some sort of combat buff against vampire-led armies.)
Anyway, back to Elder Kings: The Masquerade.