You can't distribute the world build from my knowledge, ram and cpu cores is the only way to speed it up.
In the past i have exported tiled builds from WM, when dealing with huge environments, it will take a couple of hours to make a full build most of the time. But if you have the ram for it, a single build is best. You can get some issues with edges of the tiles when doing tiled builds. But you will use more of your machine with tiled builds, the work can be split even between the cpu cores.
Where are you going to use the terrain from World Machine? render it in Maya or Max?