Personally, its not that people die that bug me. I can take care of any attack without deaths or reload if I have to. It's not that the event is hard. But, it is bugged I believe or needs to be tweaked. In some games, not all, the encounters happen too much. And in no way should they stack with other random events in a city. I should not have a thief/vampire/dragon attack happen at the same time.
The random events do not stack on the walled towns, and for the unprotected towns, the events stack exactly the same as they do for any other outside location. My Braggen fast travels to Morthal the chances are he would show up with the usual crowd, 1 or 2 dragons, random animals or bandits and some Dawnguard. My second character, Aussie is shortly starting Dawnguard and I will see if she can get vampires instead of Dawnguard. Braggen does get Vampires spawning in the walled towns, but everywhere else he seems to get Dawnguard.
I would presume it is either the difficulty level you play on, how you play or what you have completed that determines how many of the random encounters you have stacking up.