I've been adventuring in Solstheim for quite a bit now. I've even fast traveled. I have yet to see the random Vampire attacks. Does Solstheim have the vampires? Have others encountered Vampires in Solstheim?

I do not think I've even seen a vampire out in the wilderness after my Nord buttocks

There arent any.

Dragonborn Locations aren't subject to Random Vampire attacks. Probably because of it being released post Dawnguard. There MAY be a mod that adds a couple, I'm not sure.