So, he says to run the satellite cables to the diplexer but to run a seperate cable from the OTA on the dish directly to the location of your receiver?
OK, maybe you are confusing a diplexer with a multiswitch?
You need to run individual cables from the dish to each tuner - receivers have one tuner, DVRs have two tuners. If you have more than four tuners you need to run all four cables from the dish to a Zinwell WB68 mulitswitch, then run cables from the multiswitch to the tuners. No splitters, no diplexers.
For OTA, you need to run a separate cable from your OTA antenna to the TV where you want OTA. If you need to run the antenna to more than one TV, you connect it to a splitter (typically two or four-way) and then run individual cables to each TV. If the splitter decreases your signal strength too much, use a distribution amplifier instead.