I can't visit a single town in the game without either a group of Vampire or a Dragon (sometimes both) spawning and killing a couple of NPCs before I can even react. Do they eventually respawn? Because right now I can't buy certain things in certain towns anymore and the world is getting a little emptier.

Npc who have names do not respawn. To avoid attacks in towns, at least dragons attacks, do not use fast travel or fast travel to the nearest place, like stables.

Damn, it's gonna be a lot harder to buy supplies now since half the merchants are gone, lol.