The reason for the splitter is that the MyDMX dongle is putting out a weaker signal. I haven't had any issues with this, as I've regularly run my 200-foot cable to 10-12 fixtures with no problems. I installed the OptBranch/4 into my rig to not only boost the signal to standard signal strength levels, but to also protect my lighting investment.
Really, now that I have 1, I'd like another 1. This way I can do a split at FOH to go to spots(2 runs) and to some foot lights and anything else nearby, and a run to the stage. The stage run would be split into front and back trusses, foot lights and then anything off-stage. Or, in one isntance: split to left, split to right, split to fill lights.