So… I visited Solitude and I noticed two dead Death hounds just lying in the middle of town.
Rather curious about why those would be there, I did a little research.
I found people talking about master vampire attacks inside cities which are killing non-essential npcs. I assume this is related? But there were no vampire corpses…

Yea, vampires attack citys now. But if they kill a NPC you did a quest/favor for you will get an inheritance. When Bolimund died (May he rest in peace) I got a 100 gold inheritance from a courier.

That is the one thing I am really not fond of in Dawnguard; I had to reload twice in Whiterun and then re-load outside the city, because fast travelling to Dragonsreach was spawning a Master Vampire and his gang by the gate, and Adrianne along with a few other NPCs were getting chewed out before I could get there.
Not cool. I'm still torn on whether that sort of thing is actually good being in game or not...