Personally I feel we need the Ashzara storyline before a BL invasion or before we go confront them on their turf. She is tied into the Sargeras story arc and would be a fitting bride to the BL. For all we know it could be an expansion that features both Ashzara and the BL.
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Obviously you have not played any of MoP and are caught up in the KFP hysteria. Or have not bothered to read any quests, listen to any dialogue, or pay attention to anything that has gone on story wise this entire expansion. It has some of the darkest aspects of any expansion. It just happens to be on a beautiful setting with Pandaren.
BTW Cata was WoW going back to it's roots, Hard content forcing people to work together in heroics instead of a mindless AoE est, classic baddies, back to classic Azeroth and people left in droves.