It's not my goal to discuss whether or not there are actually vampires in WoW. The Crimson Halls certainly seems to support the idea that the Cullen-crowd can get their bite on in Azeroth, maybe even cuddled up against the vampire LARPers. But even with the Sanlayn rocking the vampire thing in Northrend, there still aren't any playable vampires in WoW. (Blood death knights are arguably similar, but they still don't sprout fangs and lay the nom down on unsuspecting victims.)
Yet, people still yearn to play vampires. It happens. And I don't actually mind people playing these type of characters in the free-form style roleplay you see in Goldshire and Silvermoon, because that tends to be the sort of place where anything goes. And I'll admit. In a former life I've LARPed a vampire.
But in troupe-style roleplay, there are usually particular character conventions. A roleplay guild focused on defending Ashenvale from the encroaching Horde, for example, would have some trouble accepting a Draenei Shaman who is actually roleplaying an apologetic ex-Eredar making amends for his crimes.
It falls on the leaders of these troupes and guilds, therefore, to talk to the person playing an outside-the-box character. You don't want to just leave your junior vampire going down a bad track, leaving him without folks with whom to roleplay. Even worse, it can lead to backbiting, disruption in the troupe, and other negative things. Roleplay groups are fragile enough -- don't leave a wingman hanging, when you can help them with the trouble.
Take a look behind the jump, and let's see how you can help bring an Edward Cullen back into Azeroth, while still making everyone as happy as possible.