Warlords of Draenor hotfixes have been published the 12/15/2015 ! Here is the patch notes :
Patch 6.2.3 Hotfixes: December 15 (Source)
- Guild Challenge completion credit for guild groups in dungeons and raids are now only awarded when completing current-expansion content.
- To offset this change, Guild Challenge completion credit no longer requires Dungeon Finder to queue for the dungeon. This means guild groups can now complete Mythic dungeons for Guild Challenge credit. Additionally, the gold awarded for all Guild Challenges has been increased by roughly 50%.
- A discussion for these changes is available in the forum thread: Guild Challenge System Changes.