TL;DR: Pathfinder as a unit is not OP, but the Airborn build order of 4x Pathfinders, into echelon zooks, then .50 cal and a forward ambulance is an early-game horror for axis. This is only a valid strategy when all these units are together and never split.
You have opened several issues.
Are simply badly designed.
These reckon units need a better design where they should be support unit relying on utility having low Pop so that they can fit into to an army composition but not substitute mainline infatry.
They come with 2/3 elite carbines that are very good close range and 2/1 scoped carbine that are good long range. This weapon should not be mixed. They should have only long range weapon so they become vulnerable at close range.
The critical kill mechanism need a redesign since it become silly in unit that can be spammed. One could try making the scoped carbine an upgrade (similar to JLI) and the critical kill a timed ability for all jli also (maybe with mu cost).
There XP value is too low and they gain veterancy too fast.
The beacon is a nobrainer ability that needs a better design.
2) Forward reinforcement/heal points
FRHP including ambulance in my opinion are available too early and too strong and they are one of the main reason why camping has become a good strategy.
I read some post claiming that flanking is difficult due to maps design but imo FRHP point contribute much more to the issue.
Imo one could try a number of solution like reduce healing auras and adding a reinforcement speed penalty when used outside base.
Some of these unit could see further changes. For instance Opel truck fuel cost remove but now can heal only in base and passenger, Bunker can not be use both upgrades but command bunker heal occupants (maybe create medic kits).
And then there is the scott that is simply too difficult to kill. One should at least remove the defensive smoke from the unit.
One could also try two firing MODs one ballistic with long range but slow projectile suitable vs static targets and one direct fire but with sorter range.
Other than that, I think that stock early-game USF options need to be looked at. M20 still taking years to build, despite 221 doing exactly what unarmoured M20 could be doing but 2 minutes earlier. .
This is a problem a continues buffing and can not be solved with more buffs. Actually things need to be slowed down instead of speed up and if there is a need for such a change it is the faction that need to be delayed and not the USF that need to be speed up.