Im not surprised , this is something that seems to be a problem for all direct guitar solutions , modelers and the kemper , struggle to get a good tone on stage using monitors .
I used the pod for years this way having to run it through a regular tube head power section and guitar cab and then the tried the axe fx had same issues monitor sound sucked
, the monitors sound like sheet for guitars thin and whimpy . , the kemper might work great out front , but hard to play and feel inspired unless the guitarist hears a great sound back at him on stage , so its not something to do with the kemper .
I went back to using real tube amps live, and since i l play only small venues it works , if i ever do large ones , ill use the kemper fed directly to front and the monitor out of kemper (cab off ) to a tube power head and guitar cab (2x12 so i dont have lug 412 ) seems redundant but works !
otherwise i seem to struggle with eq for hours trying to get a decent tone on stage using monitors etc
the amp i use is not a precious marshall or mesa its more of a workhorse with a great tone so i dont mind beating it up traveling around , an ampeg vl1002
just my 2 cents