ok so im sure this has been asked before but im curious about this. I have heard plenty of people complaining about the vampire raids where they kill all of the npc's, but i have never had this happen to me, i started the dlc and played as the dawnguard and completed it and have never had this happen to me. anyone have any info on this?

It is a random event and people have had trouble with random events initiating in the dlc.
It's the same with the werewolves

Some ppl have problems with excessive attacks (like me) others don't....could be a glitch in the random generator...we really don't know

yeah i kinda want to see it happen but yeah dawnguard has so many bugs they need to patch it like asap

My experience with "random" in skyrim is you either get it all the time, or very rarely....not much in between