Can you hear the mic input through the headphones when using the Prime 2?
I doubt it, because you certainly can’t on the Prime 4.
There is a feature request for this, if you’d like to add your vote to it.
Dunno why it was ever designed that way myself.
Denon DJ say many of their staff are DJs, and yet someone decided to exclude the mic signal from the headphone ‘master’ signal - and nobody flagged it?