Blizzard's focus is, as they've repeatedly professed, "to create the most epic gaming experiences ever." But for all the world-ending threats we've encountered in the last few WoW expansions, Azeroth just isn't that big. The entire Eastern Kingdoms are about the size of the island of Manhattan. We're made to believe that hundreds of thousands to millions of people of various races inhabit the planet, but examining the amount of residential space in each zone shows us room for far, far fewer.
Now, yes, the Azeroth we see could simply be an abstraction of some other, larger, "real" Azeroth that doesn't tangibly exist. But this one is the one we get, and it seems sillier and sillier each time when you ponder things like where exactly King Wrynn managed to find a hundred thousand troops to send to Northrend, or where night elves have lived for the past ten thousand years. The same goes for Azeroth's endless supply of doomsday villains and the cultists they inevitably find to do their bidding. They had to come from somewhere. And they definitely don't live in Stormwind.
But the problem isn't even really where they live. It's how they live. It's where they come from. Outland presented a unique opportunity to show us the how and why of the many strange alien races on an entirely new planet, but we learned more about how they died than how they lived -- the fate of most non-player races in World of Warcraft. Their homelands were a theme park, a casino, and we run through pulling levers, grabbing drinks, buying t-shirts. Nobody lived there.
Pandaria, though? People live there. The continent feels more like a brand new planet than even Outland ever did.