I can only speak of what I played so here goes.
First off, Warhammer Online, imho hands down the best PvP MMO ever. Epic large scale fights (hundreds of people), great 6-12 man fights, good 1v1 fights as well. For a heavily PvP oriented MMO, it even had decent PvE. Warhammer Online unfortunately never had playable Vampire Counts, although I do think there were a few Vampire models/assets/NPC's in the game. There was also a moba spinoff (Wrath of Heroes) in the work, which had Red Duke, but it didn't get past beta.
The game managed to survive after it was officially shut down and is living on on a private server. I don't think they have plans atm of adding more races, but it is not entirely impossible I guess. They have done a great work of rebuilding the game mechanics and keeping things fresh with their own additions, so one can hope.
Meanwhile, the closest thing to a Vampire would be a Dark Elf Disciple of Khaine (class designed specifically for the (original) game). I mained one through my whole War Online time and it was damn fun. It is basically a hybrid class - combat healer that needs to hit to be able to heal. Even more fun is the DPS spec which can actually heal by dps-ing if done correctly. So it has that blood link/life tap/lifesteal aspect to it that is characteristic to Vampires in general. The design is also quite similar to some of the VC designs so with correct armour pieces and colours (the game allows you to paint armour) you could resemble Konrad or Isabella for instance (the heal spec uses a sword and a chalice, while the DPS spec uses dual swords). Concept art examples below:
View attachment 61097 View attachment 61098 View attachment 61103
Next up is World of Warcraft. Altho the game is in a not so good state atm (both the turmoil in Blizzard and the bad game design lately), it should be mentioned. Blizzard always liked to draw inspiration from Warhammer and this is no different. In the current expansion (Shadowlands) they introduced a vampiric themed covenant (Venthyr) that your character can join. You can unlock very VC looking armour sets, especially similar to Blood Knights/Kastelai aesthetic. Most of the NPC's in the zone are Vampires or Gargoyles. They aren't a playable race, but since they add allied races along the way it is possible these will become playable in some time. Until then, probably the closest thing to a vampire would be a human or forsaken (undead) Death Knight since they can control undead and use blood magic. Also the zone (Revendreth) of the said covenant is one of the best zones I've ever seen in an MMO and if the player housing existed I'd be all over it. Examples of Venthyr armour sets and the zone below:
View attachment 61099 View attachment 61100
View attachment 61101 View attachment 61102