The receiver that gets hardly any HD channels probably has a faulty or even missing B-band converter.
You are going about tuning the dish the wrong way. Ignore what channels you get. You can't tune the dish for just certain channels, that's not how it works. Use one receiver only. Rotate the dish until you get peak signals on the 101 transponders. Ideally you should use "dithering" to find the center of the 101 beam. If most of your 101 signals are not high 90s or even 100 then adjust elevation, again ideally use dithering. When your 101 signals are peaked, with high 90s/100 on most transponders (some carry spotbeams and will be low or even zero) then look at 99c, 103ca and 103cb. If your 101 is not peaked, there is no point in looking at 99c/103ca/103cb.....
With a properly peaked dish, 99c/103ca/103cb should have ALL transponders in the high 80s to mid 90s. Ignore 99s and 103 because those are all spotbeams.
If your 99c etc signals are not high 80s or up, use the FINE TUNING controls on the dish until you get them correct.
I still think you should get DirecTV to do this....the $50 callout charge is good value..