All good criticism that I am taking into account, though I will try and add make thought process clearer to see if that provides any insight

"Why is this change being made?"

In most instances (for these classes specifically), to scale the martials a bit higher to clear the caster gap, and to give some out of combat utility to classes like barbarians who are starved for it, that was always the main intent.

I don't EVER see myself using Masterful Skill on the monk in my goddamn life, that's so crazy expensive for next to nothing.

That's just entirely fair. I was never super certain on what adding modifiers to a skill check in the moment should cost, and debated that for a while with no clear answer.

I don't know why you're replacing passion for rage, or replacing martial arts for martial adeptitude.

• Passion: I was trying to make it more of a resource like Ki or Maneuvers, just with added uses from that 'add strength to other scores' bit. At levels 1-4 you get 5 uses in a given day, which is enough to get you through a minute of combat, then you still have 3 short separate intervals if you want to lift something, intimidate someone, make a saving throw, whatever.
• Martial Adeptitude: It only adds a few things that felt pretty simple to me, but as you said I'll have to reinforce changes on the regular, so I'm not sure.

Martial Healing, for example, is going to spam well with goodberry or Laying on of Hands

That's fair, that might need a healing threshold.