Spawned the Spirit Elemental in Crypt of Decay for Mage 2.0 the other day and noticed he had MOTM on him. Is this a bug or by design? I havent seen any other epic mobs with motm nor do any raid bosses post PoP so this seemed odd...
A few things got inappropriately tagged with MOTM when they went through the zones, if you submit it in the bug report section of the forums can maybe get it fixed in a later patch. For now though you are going to have to deal with it when you see it.