I also just setup a renderfarm for UE4. While it works pretty well the distributen is very uneven. Don´t expect it to be like non realtime renderers where 10 additional nodes will give you 10 times the speed. With 12 nodes I roughly get 3 to 4 times the speed compared to a build just on my workstation (speaking about larger Architectural Projects). It might be different if you have a huge game world. I made a post about it here.
There is a screenshot of the distribution. As you can see most agents finish quite early while one does the main part. Still wonder if this can be tweaked ?