The problem is you can't afford a PIV and a StuG III, the PIV locks you into having a unit putzing around that doesn't scale well when facing off against heavies/advanced tanks like the ISU/IS2/Churchill variants/Comet/Easy Eight/T34/85 because it's pen is sub par for what your paying for.
Basically a lot of the issue lay in Ostheer T3 being very expensive, and the USF 75mm low velocity Sherman having the exact same pen for lower cost on it's AP shells with the added bonus of the ability to switch to HE shells that are great for wiping low model count Ostheer squads right off the map.
The solution lay in two things; either making the PIV better in pen or something else or lowering it's cost. It was suggested in the other thread putting the Ost one at 115 and OKW at 125.
I fail to see how the P4, which has some of the best vet in the game does not scale well. I also fail to understand why a tank generally shooting at lower armored units needs more pen (the sherman always shoots at higher armored targets so of course it needs equivalent pen and even then it won't do as much damage). I also don't understand because it comes with an MG upgrade that improves its lethality against infantry. Flank?
Easy eight and 85 are both doc tanks and both are designed to deal with other tanks. P4 still a threat to them but you are correct, they are better. That is by design. If your opponent uses them get Stugs not P4's. P4's are good at everything excel at nothing. E8 and 85 are very good against armor, ok against infantry (excusing random squad wipes from clumping).
You complain you cannot have a P4 and a Stug, and yet mention the problem is the ISU/IS2/Churchill. If you cannot field a P4 and a Stug by the time these units come out you have lost that game. You should never be so fuel starved. If your opponent may go churchill and you feel light on AT build a Stug first.
But no other army in the game has to make this sacrifice. Conscripts get AT nades, molotovs, better veterancy, and doctrinally they get an AI upgrade. USF can put basically anything on it's mainline infantry (and doctrinally add the ability to put down Schu mines). Brits can also put any variety of upgrades they want on their mainline infantry as well.
Simply put, Volks are the only basic infantry in the game with neither a doctrinal upgrade or a selection of upgrades period. This of course isn't getting into the fact Volks scaling got a huge kick in the nuts with the Conscript and Rifle scaling buffs.
I don't know what sacrifice you are talking about because you are too vague. Every basic infantry unit has to make a sacrifice.
Volks are cheap, cheap to reinforce, do not require tech, and have excellent abilities. They also salvage, build green cover, and never require fuel costs to upgrade directly (excusing tech to unlock their AT weapon). They can be helped with a doctrine. Shreks are also lethal against infantry especially at close range, and do not reduce infantry killing power except at range where they will miss frequently. At that point they come with the added bonus of destroying the target's cover.
Just because you don't have something in your faction doesn't make it a bad faction, it makes it a different faction. Rifle and Scripts got scaling buffs because they simply could not manage to be cost effective in the late game. If you are expecting volks to shred Rifles and Scripts like they did before, think again. Now cover and intelligent flanking is still required in the late game, and dependence on your AI squads. Volks are good at lots of stuff, but exceptional at AT, you don't also get a punishing AI unit.