Considering the thread is called "Caster DPS legendary weapon" and the post he replies to says it is a Caster DPS Legendary Weapon, and the fact that the only other DPS Caster legendary has been removed from the game and was available from a raid instance a tiny amount of the playerbase actually saw, it would make sense, especially considering that Atiesh was a caster AND healer item.
Really? A Mace? I would find that pretty hard to believe since the two Pure DPS Casters can't use maces, meaning you drop the amount of specs who can use it down from 9 to 3. Still, as you say it's better to wait until we get some real information.