This alternate timeline story already gave me a headache but it gave me a migraine when I thought of this:
The Burning Legion transcends all realities. The Burning Legion you get is the same every time, that means ONE Kil'Jaeden and ONE Archimonde.
The problem I have with that is, they weren't the only sons of whoever gave birth to them, we also have Velen.
We have at the very least two Velen, and the WoD one sacrificed himself for us. It's safe to say that there are more Velens out there.
Considering the fate of the alternate characters we met in WoD aren't THAT far off our timeline, surely Velen in other realities must have two siblings, Archimonde and Kil'Jaeden or whatever their names were before they turned Eredar, who give in to the offering of great power, soooooo... what happens to them? Considering the Draenei in WoD seem to have fled from the Burning Legion as well I don't think the answer is as simple as "The BL didn't bother with the draenei in other timelines".