Ok, first off this is not a question of the time logic or any of that fun stuff. This is simply to ask how does Garrosh get the mojo to not only send himself back in time but also send him to Draenor.
From what we know right now only really two groups of creatures really know a lot about the time ways; bronze dragons and the faction of people found on the timeless isle (I forget what they are called). Of these two I don't believe any of them currently possess the ability to actually travel or send someone else into a different timeline. I think at the most they can currently view different timelines.
Also the order these things would have to occur is very important. Garrosh could not just travel back in time then go through the portal he would have to first be on Drawnor then travel back as the portal did not exist at that point in time (yet).
This brings up the possibility of him finding some unknown power source in outland (warlock green fire quest, *wink, wink*) to supercharge some sort of time device (timeless isle quest).
Any thoughts on how he may achieve this?