A mistery? ... nice understatment!
In Premiere Pro its so easy.
I just set up a sequence with adaptive 4 tracks and adaptive 4 master out, then map the tracks to the outs by simply checking the cossesponding boxes of the routing-matrix... thats it.
But I would like to get rid of Premiere

Ok, simultaneous monitoring is a problem, I get it... I could use an atomos shogun for that, no problem.