What I thought was very lacking, is that there was no direct threat to the world.
In Cata, you had armies running about trying to beat eachother and Deathwing just about everywhere (With the exception of Uldum which was just some 'discovery' for the Indiana Jones crew)
In BC, you had outposts fighting demons on their borders
In Wrath, you had fucking undead and MASSIVE (See Warsong Hold) outposts fighting undead and other races loyal to Arthas all over the place.....
In MoP, we have 2 large threats: The Mogu and Mantid. And what do they do? The Mantid have an army that sits idle basically slapping you in the face if you run into them. Why aren't they fighting the Klaxxi? Their air forces get shot down every time I fly to the Dread Wastes.
The mogu, a nice big empire with an island that has fucking lightning striking down wherever Lei Shen wants, with an army in their courtyard. And just like that, Blood Elves and Kirin Tor stand on his doorstep as if he doesn't notice them. Where is the warcraft? Where is the direct confrontation? The only real Warcraft we get this expansion is in the Jade Forest in a cutscene, and in a raid which is called Siege of Orgrimmar.
The most fun I had in the expansion, was in 5.1 where both factions had some decent lore involving one another. But now.... there is... Horde attacking Orgrimmar and Alliance pop out of nowhere to the rescue....