A couple questions with this requirement:
1. If unlocked for one spec, does it unlock for all the other specs as well, identical to the hidden skin?
2. Does the above apply to the other skins as well, such as killing Heroic KJ?
3. What bosses are required to unlock the skin?
4. When the next tier comes out, will the requirement for killing Heroic KJ change to the Heroic of the last boss of that tier?