their default form is just pale with glowy eyes. this special ability is far more interesting from a gameplay perspective imo. How exactly would it be fun or make sense to lay in wait under a single lake, hoping a random npc appears above? the mist thing is kinda neat, but the bat cloud is similar anyways. and wings aside, is more of a throwback to the original movie vampire appearance.
http://upload.wikimedia.org/wikipedia/commons/thumb/5/5e/Nosferatu-movie-poster-11x17-large-style-c.jpg/220px-Nosferatu-movie-poster-11x17-large-style-c.jpg
As a player character you wouldn't just hang out under a lake. But it's still do-able. To simulate their icy grasp, you just add frost damage to unarmed attacks, or give them some touch frost spells.
And they could effectively bring back waterwalking, giving them the ability to freeze the water they walk on, & even move through all of the various solid sheets of ice in the game.
And hey who knows, maybe they'll do something with it that will make it less than awful, stranger things have happened.
I do however entirely fail to see how their visual design is a throw-back to Count Orlok. And Orlok is the Nosferatu you're referring to. Even disregarding the wings they look nothing like him. Tall, emaciated guy with facial features reminiscent of a rat, claws & a slight hunchback /=/ giant hulking monster, with a body builder physique, & an enormous bat head.