We have decided to remove the added bonus of gaining Guild Experience from Guild Achievements earned. For guilds that are currently above the normally possible experience limit, we will be readjusting it back to the expected limit once more. This will not affect Guild Reputation gains at this point in time.
This did not stay in affect, there are level 2 guilds from having done achievement runs of Wotlk dungeons, and my guild is stuck at level 1 where all guild should be until tomorrow at the earliest according to the guild exp cap.