Not unexpected. At this point in the storyline, Garrosh is being the ultimate butt and everyone's pretty distracted. What does this mean for Alliance looking to complete the For the Alliance! achievement if there's no Garrosh? Sure, there will be a new leader to kill, but we really can't guess when the achievement will be updated once patch 5.4 hits.
If you can gather a group before then, do so! It's unfortunate that Orgrimmar can't be cross-realmed -- this part of the achievement must be completed with people from your server. To avoid being caught and overrun, arrange the raid via social media or within your guild. Word spreads quickly when these runs go public. Good luck!