Alliance fans aren't ready for the Midnight twist where the void plot is finished by the end of 12.0 and Turalyon and his army of light then proceed to use the sunwell for evil.
Resulting in the next two patches being about how the death from the Shadowlands come to rescue the living from the tyranny of the light Liadrin invited in.

The optimal play is to spam Vanilla and TBC raids first because the amount of drops you actually get is already abysmal.
In fact, I'd even say make sure to get Battle for Hyjal fully farmed out the way first, so you never have to suffer it again with it's vanilla drop amount