Classic vampires are pointless (though not toothless) in this game. There are already vampiric attacks used by creatures and players leeching strength, whether HP or MP, from their targets. Having a player race that literally sucks/consumes the blood of other beings is entirely unnecessary, and IMHO doesn't fit in Eorzea at all. How can a vampire who classically preys on other people also be the Warrior of Light who's in effect the champion of Eorzea and 'sworn' to protect her people?

Sorry, but in a game without blood (thank goodness) during combat, I fail to see how the addition of blood sucking monsters as player characters adds in any way shape or form to the existing lore or game. I can think of ways it detracts from what we have.

I know that this is a cliche answer, but if you want to be a bloodsucker, I am certain that there are games that cater to you, I suggest seeking them out in order to vent your need for that kind of gameplay.