From all the times i've seen mind manip in fiction, most of the time a verse has grand scale mind/soul manip it's treated as the same potency for everyone evolved, similarly to casting a mind control spell in multiple foes and having them all perform the same mind resist check to see if they got affected or not.
The best 2 examples of explicit quantity of people haxed = potency i can think of as of now are
Cosmo's mind manip in chainsawman, where she overloads a target's mind with massive amounts of information, wich allowed her to defeat a character who resisted mind attacks by sharing the burden with many proxies, and
Psycho helmet/Gdimple's divine tree mindhax, that amplified it's power with each new consciousness added, eventually bypassing even strong espers with good mind control resist.
However, i still believe quantitative should be used for the simple fact it's the most objective way of defining mind hax potency. At worst i'd say we try to make the standards for range x actual potency harsher.
One of the few cases i do believe that quantitative potency shouldn't be used at all is when the mind control is achieved by "affecting the hardware in order to mess with the software" a.k.a messing with the brain's biology/anatomy to achieve a certain mind command effect, like a character releasing a virus that turns people into puppets, being able to biologically manip a character's brain to force a certain behaviour, releasing parasites that hijack consciousness, etc. Honestly, that sounds more like something that would be covered by bio resist rather than mind resist.