World building for a D&D campaign is tough, but world building for a novel, now that is indeed a challenge. 
My cousin and I spent a good hour and a half just making modifications and  name changes to my current draft of De-toril. 
We currently have a northern continent and the top corner of a second continent.
8 kingdoms, 4 independent cities and our next step is to break the map up into more detail sections. 
With D&D if you make a map, rip off a couple of names for cities, thrown in some mountains and  forests your good. 
Now we are making a map that is geographically logical, with unique cultures, histories, politics, and trade systems.
By the time we are done with this world it will rival that of Middle Earth and Westeros.
We are currently on draft 3 of the map.
This is gonna take a while.