The only griefer problem that can ever exist in an MMO is having too many restrictions to deal with them in-game, such as safe zones to abuse, or looting restrictions. Contrary to basically everything I hear from people who have an irrational fear of a system they've never experienced, griefers can't grief in non-consensual, no-restriction environments. The only griefing I've ever been personally annoyed by is abuse of in-game restriction features like PvP blocks, because there's nothing you can do about it.

If you can't handle some guy coming around killing you, get better at the game.