What do you think they are doing with the fields of farahlon. Its basically pre Outland Netherstorm. Its on the map of Draenor but they said that it would be added in a future patch. Im actually very excited about it. If they add it all, then it will be the biggest patch piece of land added ever i think? Here are 2 maps. I is the in game one, and one is an Outland and Draenor size comparison. It is pretty big.
In game map. Fields is the top right zone.
And here is the size comparison.
Also here is a size comparison to all of the zones in wow.
So It looks like Outland is 10% bigger than Pandaria, and Draenor is 10% or more bigger than Outland, so Draenor is probably almost as big as Northrend.