Well, it seems that Blizzard has had a "slip" and they have escaped to Val'anyr of the studio and has appeared for about 20 minutes in the armory. Enough for World of Raids to photograph the mace in question.
Here you can take a look at the mace in question:
Also revealed are the quest reward items that can be obtained by defeating Algalon the Observer en normal mode and in heroic mode.
Who do you think should take the Legendary Mace?