Professional cartographers will tell you that on a map like this, Pandaria is shown as bigger than it actually is. Projecting a spherical map on a flat pane causes that.
Most maps we are familiar with use Mercator projection that makes countries further from the equator look bigger than they actually are. For example, on Google Maps, Greenland (far from the equator) looks similar in size to Africa (close to the equator), but actually, it's smaller than, say, Brazil.
http://media.mmo-champion.com/images...onWorldMap.jpg
As you can see, pandaria is far from the equator, almost near the south end of the map, while the Broken Isles are REALLY far from the North pole, with Northrend in-between.