+13. I agree with literally every word you said except for a single sentence of your mobility paragraph.
Mobility in combat
I haven't seen evidence that enemies in general can disengage as a bonus action. Goblins can, but this matches 5e and is part of their nimbleness. And so can the jumping enemies (bulette, minotaur, owlbear, and I guess the phase spiders count?). Most enemies we face in the game will probably provoke AoOs; it's just that this Act has a high amount of goblins and jumping enemies. That said, I fully support separating jump & disengage and making disengage a standard action. Jump can be a bonus action or just part of movement, honestly whatever at this point.
I've had the humans outside the ruins disengage on me, but I feel like it's not common just because the AI doesn't optimise for it.
What i find funny is that they haven't added a single piece of magic heavy armor yet so that some chars can actually get some use out of those useless feats and profficiencies. But you have these ultra rare cheat items:
1.- Warped Headband of Intellect
2.- Disintegrating Night Walkers
3.- The Sapphire Spark
I'm honestly fine with broken items like that, being able to plan a build around them for a second or third playthrough adds a lot of interesting replayability.