If I am not totally mistaken, that wasn't Wrathion but a bronze dragon from Timeless Isle...Kairos or something like that? I am pretty sure Wrathion kind of disappeared in MoP as soon as he realized that we wouldn't support his plans any further.
Edit: Nvm, just read about it, you are right, Wrathion was behind Kairozdormu and the whole WoD disaster.