Based on the fact that when I attempt to run just the dimmer packs or just the LEDs everything is great, I went ahead and ordered a splitter (in route) and I am going to try that.
I should not have cheaped out on the cable, but with everything else for our church build out of a commercial storefront I was under a lot of pressure to go as cheap as I could.
The isolation should certainly help by keeping the dimmer packs of the signal heading to the front of the room. We even had a guitar DI'd, but the flickering was setting off his pedal setup.
Thanks for the thoughts. I spent about 5 hours on this Sat and tried anything I could, so I will see if the box helps.