while one step per turn would be an exaggeration, it does sound to me like the most likely cause is a difference in playstyle.
I would guess that the people who are struggling with it generally take more time in tactical missions for whatever reason, and the people who don't notice it tend to be faster.
I don't see a reason to penalize the people who take more time, not for the sake of better gameplay or for realism. theoretically, a longer (by a minute or two if you convert turn time to real time) and more careful mission wouldn't hurt someone's readiness more than a fast and furious one.
this is why I'm on board with the suggestions later on in this post:
https://openxcom.org/forum/index.php/topic,7775.15.htmlspecifically, the altering of readiness based on xp gained, and possibly total morale lost as well.
I plan to try and hack together something like this over spring break/quarantine if I have time.
anyone have suggestions for how to get started?
i've already got the mana and ruleset documentation, and if I remember correctly solarius said readiness is attached to armour.
anything else I should know?