I have no idea how much lighter bass you are hearing, if it is somewhat minor that might just be the DAP sound signature versus the Diablo DAC. If it is very significantly light on bass there is probably an issue and it is probably the cable.
If you are not hearing humming it sounds like cable is providing proper grounding, if you are it definitely isn't grounded.
The best way is to check with a continuity tester to see if the lower ground sleeves of the plugs are connected to each other through the cable.
I don't have that cable yet so I can't comment specifically.
I can confirm the iFi cable works perfectly.
Oddly I have a non grounded cable and it works fine with the Gryphon but not well with the Diablo .... no idea why.