The infantry hitpointsystem is set up with dependencies for various hitpoints. In all cases the "max" operator is used for "parent" Hitpoints (HitBody and HitHead in case of vanilla A3).
For example, depdency for HitBody is "HitPelvis max HitAbdomen max HitDiaphragm max HitChest". So the Hitpoint "HitBody" will have the value equal to the Hitpoint with the largest damage value out of those four.

This means that all four hitpoints combined can take 4x 0.9 damage, and HitBody will still only be 0.9. Combine this with significant armor (="healthpoints") increase from body armor and you can end up with seemingly invulnerable infantry, or people thinking that their shots wouldnt register.
While global damage should in theory account for this issue, it does not operate in any understandable or logical way. During testing, the amount of global damage received from a hit never corresponded with the damage caused to the individual hipoint (e.g. HitPelvis) and the respective config values (armor, passthrough and minimalHit). In some cases, small amounts of global damage where caused despite minimalHit values that should prevent any global damage and despite damage to an individual hitpoint (e.g. HitPelvis) beeing 0

This can lead to infantry taking a ridiculous amount of rounds, especially when heavy body armor is involved

Suggestion:
Use the + operator instead of "max".
The explosiveshielding property of the hitpoints need to be modified accordingly (for example divided by 4 for all Hitpoints related to HitBody) to account for the damage stacking in case of indirect damage from explosive weapons.
In addition, re-check how the global damage/health system works, make it more logical and document it.