I really don't think vampires, or trolls, or werewolves, or witches, or any other fantasy animal belong in Fallout....
I would argue that they aren't necessarily "Fantasy" tropes...Not to mention Witchcraft, or Wiccan, is an actual Belief System (as my Wiccan friend likes to remind my Catholic rear).
No, indeed, they are more "Horror" Tropes.
Well, except maybe Trolls. But they go under bridges. And eat Goats.
But Vampires go back into our actual History~ They aren't fantasy, they are genuine Historic Folklore.
As for people who say they "Don't fit in", I dare say, anything can be made to fit into a genre if made to serve the Genre.