There must be some major bug or they are really bad at higher levels but I never had any troubles with the vampire attacks and as of yet haven't been attacked in cities since finishing that quest. Also I've seen the mysterious traveler and if I didn't bother him he didn't bother me he just wandered around at night never killing anyone. I'm thinking the players that have the most troubles their characters are at a higher level. I lost maybe 4 villagers in the whole campaign and none of them were shop keepers or quest givers so maybe it's just bugged really bad for some people or really unlucky

Mysterious traveler?

I've had no such attacks, nor any of these travellers, and im at 81...

I only had them happen a few times in all