Greg Street, more commonly known as Ghostcrawler, is the lead systems designer for World of Warcraft. While we can never know exactly what his responsibilities are internally, we do know about his external presence: He is the authoritative voice concerning class design. Players flock to his increasingly rare blog and forum posts to read about the direction their classes are headed. There are a slew of developers working on WoW, but his words are the ones that seem to guide our fate.
In a completely unprecedented event, Ghostcrawler has been replying to dozens of posts in a Mists of Pandaria beta rogue thread. His posts are so frequent on this thread that he even had time to reply to my comment personally. He's shared several pages of information with us about rogue design in Mists, Blizzard's concerns and design for the class, and class design in general.