Lesson learned from the breakup of Yugoslavia: A shot in the pelvis is a mobility kill.
Absent advanced trauma medical treatment it is probably lethal within 30 minutes.
And it doesn't take too many pelvic casualties to completely overwhelm the enemy's medical system.
There is an armor-side solution to that - because of course the protection guys weren’t going to ignore it. Back the soft armor with something like D3O non-Newtonian impact protection foam used in modern motorcycle armor. Stuff is uncanny, but it protects against impact kinetic energy like nothing else. https://en.wikipedia.org/wiki/D3o
The most you’ll get with a pelvic hit against someone so protected is knocking them down - which is no small advantage for you - but they’ll quickly get back up and won’t need medical attention.
There still isn’t any solution for whiplashing someone’s brain with a non-penetrating hit to the head or visor.