I remember them nerfing Mirror of the Blademaster back in WoD, because some classes/specs, like BM hunters 'buffed' their damage with their mastery. BM hunters, for example, it would can only 2 mirror images instead of the default 4 of most other specs/classes. But it is still a BiS trinket for timewalks for most, if not all classes to use, the damage is still huge, low CD, long duration, can even help tanking as the bosses have high time targetting the mirrors instead of the healer or dps on casting their abilities. This Mechagon punchard might still be useful at least in TW too, must test it on the upcomming WoTLK TW.
At least as a feral I can fit this in waiting for energy to pool to refresh BT bleeds. Maybe that still makes it better than the other cards.