Which do you want: “volume”-only or “soloistic,” with all of the other aspects that entails? (This is an either/or choice.)
If you listen again you’ll hear Dorico + NotePerformer is shaping things well beyond pure loudness. It’s automatically adding in variations of MIDI velocity, thereby causing timbral adjustments well as loudness, and bringing the top line out over the lower one without my having to do anything other than write mp < mf > mp. (I did no manual MIDI controller writing whatsoever until I tried out CC7.) Whether it sounds “realistic” or not is somewhat a personal musical determination, but you can experiment with the Playback Options > Dynamics settings I mentioned above.
In using NotePerformer I am by default entrusting a lot of this to “the machine,” since to my ears it renders quite musical performances — certainly good enough for the purposes of a playback demo — without my having to futz around much (unless I’m writing jazz…). In so doing I am also “surrendering” control to some extent, since it’s designed to do so much.
As pointed out, the library makes a huge difference in playback response to things.
Others here are far more experienced in working with porting Dorico into DAWs to do the “hardcore” shaping of things, so I should probably step back now and let them offer their wisdom to assist.
P.S. — I see that you’ve also got this parallel thread going, touching on related issues: Interpretation of CC11 (expression) / Velocity midi. Perhaps you’ll get your answer there.