That was the answer we were looking for.
They've said before that devs play on the same servers as everyone else. They are however not allowed to tell players that they are devs, so it is true that some are in guilds and no one knows who they are.
The majority of the studio play on the 'official' servers on pretty much a daily basis. We aren't allowed to say what our character names are or even that we work here to our guild-mates, but we do play... Some of us more than others of course!
We even have mini competitions between ourselves to see who can play the most of the most things.