When I run my Proto 2000 ABBBA PA/PB's (still all DC, center B unpowered) in their lashup, they run like one engine even with a long train of coaches behind them. Very little to nil hunting, even between that dummy. They are so evenly matched it seems impossible, but that's the way they are. And that's the secret to consisting in DC. All the same brand and drivelines will usually be OK. It's when you mix and try to match brand against brand, gear ratios against gear ratios, that mismatching could occur. With DCC you can adjust the CV's to even things out, not always easily and across the speed ranges of the individual locos.
I think you may be confusing having 2 DC engines on the same track and having 2 independently controlled DC engines on the same power block. That is not possible, but 2 or more all controlled by the same cab, is.
Several locos come with 2 motors, Athearn Genesis' DDA40X and now Bachman's as well. The Genesis has 2 synchronised decoders, 1 for each motor, even begins the diesel motor start-up sounds sequentially. Proto's E8/E9's are the same and I'm sure the Gas Turbine would be likewise, even if the motor sound is singular. Most DCC/sound locos have advice to wait for the motor sounds to drop back from start-up to idle before attempting to move off, probably to help with the increased current draw that all sound decoders require to get the sound going. I have a Kato SD80MAC with ESU Loksound that is programmed not to move till the start sequence is finished.