It feels less engaging to me because it's one less factor to even worry about as MCH, doubly so for AoEing (since pushing for overheat then is a damage gain, especially when you snapshot flamethrower). It should always be a factor for balancing in general.
If adjustments are needed, you're better off making small changes like value to see where it lands you. Change too much at a given time (readjusting potencies, readjusting buffs) can lead to a power increase that eclipses their peers (looking at you, AST and BRD) and now you either have to nerf the class, or buff their peers so they're all relative. The latter of course is going to cause an outcry, no one likes getting nerfed. The latter will cause current content to be undertuned, and future ones will have to take that into consideration and start escalating.
As far as the job mechanics are concern, they all lay out a good foundation that can be adjusted and expanded (except for MNK to a degree) by adjusting values such as durations, stacks, potency, etc etc. Giving hotshot a 3% buff is a way to increase MCH's overall damage without too many other factors getting in the way. Adjusting heat values means you're seeing less cooldowns, on top off affecting MCH's core gameplay around that. Something like giving Reassemble a lower cooldown, or increasing overall potency based on heat is hard to quantify on paper, and I doubt it's really addressing any QoL concerns either.
Being aggressive is exactly how they managed to have very little (if any) net gain in performance. The heat changes are arguably unneeded, and it's caused a drop in damage output because you're getting less cooldowns because of it. And that's just speaking from a damage perspective, the already small group of MCH players is incredibly divided on how it's affected the playstyle, and seemed to have addressed the wrong concerns with heat (overly punishing for overheating improperly, rather than being too easy to overheat improperly, for example) If you start adding more and more changes, you'd need to take into consideration to how that spanner will interact in the gearworks, something I'm doubtful (given their trends) they can fit in a midpoint patch.