I'm not an AD user, but this applies to all virtual drum instruments...
The sole function of any drum sampler's master bus is exactly what you suggested: for doing all the mixing within the instrument and routing the whole thing out to a single stereo track in the DAW.
Personally, I prefer coming out from the instrument's busses to individual tracks, e.g. grouping all the toms into a common bus within the instrument's mixer, then sending that tom bus to a "Toms" track. That yields the best of both worlds, plus it allows me to freeze the instrument and still be able to tweak effects afterward.
I don't think I've ever had a need to use the master bus in the drum sampler's built-in mixer. I suppose you could put a compressor on the master for parallel compression, but that seems like a very clunky way to go about it.