Blizzard has changed IDs for some guild raid achievements and their criteria, so we are updating those achievements with new IDs in order to fix this issue. Thanks for reporting it.
P.S. You can see that even armory is giving strange data for guild achievements:http://us.battle.net/wow/en/guild/cairn ... 5079:15087
It says that you have completed Throne of the Four Winds but when you click on the achievement it gives "checked" mark only for Al'akir.