I believe a separator can only be used on the 2 inputs of 1 dual tuner. Band splitting.
You should be able to use a separator on each of 2 ports of a DPP44 to feed 2 722s.
Port 1, used for power input can be on 1 of those lines or on its own line to the power supply.
I have had 2 722s and a 622 fed from the DPP44 on 3 lines one shared with OTA. Hopper now.
-Ken