Get the fog service installed on your images and you can skip the joining to the domain step (with some additional settings in Fog Web UI).
I would increase the queue until it starts affecting the imaging times of the machine by more than a few minutes. It’s really subjective whether you want to do 10 computers every 25 minutes, or 15 computers every 38 minutes.
With a good disk subsystem and raid controller, you can push the server to it’s limits.
For my setup, unicasting is actually faster than multicasting, and much more reliable.