Well, unless he pulled a Kairoz and got a powerup through third party means like Old God juice or something.Cataclysm actually. Basically, the idea was that there was only 'one true timeline,' at least in the sense that all major events have to happen, or things go out of whack, badly according to Aman'Thul. Nozdormu was in charge of making sure things didn't go off too much, and even led the effort in killing his Murozond, future Old God slave self. But then the writers got sloppy and had the Aspects loose a good piece of their power with Deathwing's death, meaning that Murozond shouldn't have been powerful enough to cause all the havoc that he did.
But yea, I was mostly thinking about the Garrosh trial where the people of Azeroth had to fight their time displaced alternate selves. Like Thrall fighting Slave!Thrall, or Kalecgos fighting Malygos!Kalec, or Anduin fighting Shinji!Anduin.