The Jackson is literally the top of USF AT, then there's nothing for a long time until Bazookas and AT-guns come into play. The JP4 is the counter to the Jackson, however both are tank destroyers and should inflict reasonable damage on each other or else there would be no point in building one or another. If you fear the Jackson becoming OP just compare it to the Firefly.
So whats the top of the AT for ostheer? Whats ostheers answer to the jackson?
The Firefly is already a problem for ostheer to deal with due to its high accuracy, range, and damage. However, it can be dived far more easily that the jackson because it has half (1.6 opposed to 3) the acceleration and -1.2 the top speed of the jackson making it hard to kite with. Brits also don't have rifles with snares preventing chases. THAT is why the firefly has the standard 640 HP. It also costs more and has a slower rotating turret.
The Axis have something called Blitzkrieg or Combat Blitz, both offer tremendous buffs to mobility, survivability and in case of Combat Blitz even accuracy (+100%). Once these units give chase to a 200hp Jackson not even a snare will save you.
a 15% top speed boost and 30% increased acceleration aren't what I'd consider "tremendous buffs to mobility. HVAP increases damage AND accuracy which offsets the survivability part o blitzkrieg.
Also, since when did 600hp-200 dmg from a tiger/panther = 200hp?