Having finished up the quest series and progression to level 100 on the Beta server I can honestly say, without spoiling anything, that not a god damn thing happens plot-wise.
While I did not care for much of Cataclysm I have to admit that the places you go and the process of levelling up during the quest content was at least quite interesting especially with all the Elemental Plane business. I found Pandaria to be a nice return to "explore a new land" with some strong story elements about the Sha and all the philosophy of the Last Emperor and all that. I know some people did not care for it, but I thought it well done and certainly made me hungry for chinese food everytime I went to the Valley of the Four Winds to do the cooking dailies.
By the end of WoD release content I don't feel like much happened. There are some "events" that occur during the process but I did not feel terribly invested in the characters or what was going on as precious little is really made clear during the content of the game. I kept feeling like there was a whole subtext of information about what was going on that I just was not seeing.
I think I spent more time adventuring with and questing for the Dark Iron Dwarf engineer than I did Yrel or Maraad and for many of the zones my reaction was "wait...what?" in terms of what was going on. Most of the quest content was "hey we're setting up an outpost in the next zone, go there and oversee construction" and then breadcrumbs that extended from that but which ultimately didn't really do anything. Looking at the map I really have to struggle to remember what happened in Gorgrond and Talador as they were especially unmemorable. The "end" is in Nagrand but otherwise the place felt like collecting lots of bear-asses. Spires of Arak was the most interesting zone, in my opinion, but also the most self-contained plotline which had nothing to do with the Iron Horde.
Shifting the capital to Ashram was ultimately a bad idea simply because I am far more invested in my Garrison than I am the "capital" way the fuck over in PVP land and feel somewhat annoyed that I have to port or fly over there. If my capital was in the same zone as my Garrison and was in-fact the city of the local population it would feel a bit more organic to go there for services that I lack in my own town. As it is I've been charged with setting up the Alliance main outpost in Draenor and overseeing sub-outposts all over the continent and yet there's this whole other BIGGER "Garrison" that exists over in Ashran. Kinda tosses the whole narrative out the window.
I like the Garrison and I think by the end of the release content they have a stable launch-pad for additional content that moves the story along. But you spend a lot of time for what feels like a very drawn out prologue.