you would assign a track in the DAW to a stereo pair of outputs on your sound card and run those to two of the channels on the mixer panned Left and Right.
then in the DAW you could pan that track to its realitive outs. I suppose kick, snare, bass, vocal, could have thier own mono track...
I'm just trying to picture a typical mix, and it seems there would still have to be summing in the DAW. Not as much I guess.