Couple of things here. You tire me with your fan boy comments. You also cannot use attack ground, as was already pointed out, because the JT will fire at 60 range, you must close to 40, and then when you do he continues to back up since you have to stop to use attack ground.
All theorycrafting aside, I ONLY give advices I actually used in the game. 60 Range only works with a spotter and the problem you describe only concerns medium tanks, which are NOT the counter for the JP4.
I use always double AT guns, and have destroyed countless cloaked JP4's in that way. If you don't manage to do that, its not my problem I'm perfectly capable doing this and so is every other player then.
Overperforming units do not get a pass because the faction is weak.
And by what do you define overperforming? To use this terms you need to do calculations which then prove your point. I don't use the word therefore. Its lethal to tanks and weak to its counters (At guns), while costing a respectable amount of resources and opportunity costs due teching. No over performance here.
How do you hunt down an invisible tank in a faction with the most handheld AT, forward retreat points, and the cheapest and also cloakable AT guns again?
You don't need always to destroy tanks in order to counter them. All you handheld at and raketenwerfer won't do anything against 2 at guns. Keeping units at bay or shut their play down means to counter.
JT cloak is stupid as it is implemented. I like the mechanic, but the recloak rate is crazy fast. It is already extremely hard to hit (small target size), has amazing vet, can spot for itself, is relatively fast cloaked, and is available very early. The damage bonus at vet 5 is outright stupid, it already fires ridiculously quickly at that point and with the bonus damage it nullifies everything on wheels/treads. It should receive high accuracy and penetration out of cloak at vet 5.
It's one of the units that hasn't been nerfed into the ground yet. Which still keeps the stats and bonuses relic once had in mind for OKW with their vet 5 system. In addition its an important crutch right now and it needs all the survivability it has right now, since spending 135 fuel in mid game also means high opportunity costs, since you can not tech for obers or get any anti infantry vehicles out soon. Hence its survivability needs to be higher than the tank destroyers of other factions, because OKW can't pump them out like other factions.