On the Hobby Factory
Designing a campaign setting (much less one you are preparing for playtesting for pre-publication) is less like trying to build a car, then it is trying to assemble all parts of the car simultaneously without assistance, mechanical or otherwise.
Just a short selection of the inter-relationships of a single area that must be dealt with. . .
Random encounter tables, requiring a NPC party generator, faction descriptions, new monster descriptions and dragon generator. Monsters requires a trinket generator for items found on the monster. Each area requires its own rumor tables, treasure maps, and faction quests. Each area, requires that you are aware of every connected node to the area. And this hasn't even begun to touch the actual design required for each area. All these things have to be functional, unique, and interesting for each area.
It's a lot of work.
The payoff? Being calm, collected, and having your players be very, very, certain it is their own fault that their characters died.