Originally Posted by
Sondrelk
I would imagine their thinking on it was:
"Hey, we are planning on making yearly expansions, so now is the time to come here with your ideas that would not normally fill an entire expansion"
"What about time-travelling orcs? We have a bit of extra PR for the movie that is starting production soon, and players loved TBC, so being reminded of it should be good"
"Perfect, let's do that"
Then the idea of yearly expansion failed, and Blizzard realized that they had to make do with what they got and move on to Legion and hope that the scraps they had left for WoD was enough to tide players over for Legion. Otherwise the risk they were running were falling behind in quality each expansion and losing more subscribers each patch.