Sleep through doing the Queue yesterday? I can't go for that. But I did.
Am I alone in thinking that Garrosh will go back long before the drinking of the Demon Blood? By the point they drank, the Horde was already created and using fel magics left and right in the war against the draenei. They were all already green corrupted orcs unless they were in some isolated place like behind the quarantine of Garadar. The drinking of the blood was the final touch to fully bind them to the Burning Legion, just before the sacking of Shattrah near the end of that war. Garrosh has to stop Ner'zhul and Gul'dan long before that.
I believe it was stated during the story panel at BlizzCon that Garrosh goes back to a few (2 or 3) years before the whole blood thing. The draenei are still around at that point, some key decisions haven't yet been made. It's more ripe for story fun than arriving at the moment Grom's about to chug some blood.