A balun has NO application to TV in this context.
Diplexers are NOT for combining/splitting two satellite signals. They ARE for combining/splitting ONE satellite signal with a TV RF feed such as a receiver's output or an OTA antenna feed.
Two feeds are REQUIRED for the 522, but DishProPlus technology can allow you to put them on a single cable. A DPP44 switch or DPPlus Twin LNBF is used to drive a DPP Separator.