I think that penals are over performing at. Aggressive AI into defensive AT is a fairly risk free transition. You have a strong unit to beat the enemy infantry and built in defense against the usual counter to AI infantry.
Ideally I would have their price reduced and spawn with Mosins with a munitions upgrade to either SVTs or PTRS' as this slows the early game pressure (and improves Soviet map control slightly) but also makes a choice.
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I'd not say penals are overperforming. They are stronger than most mainlines, yes, but they cost 300MP, so they should be stronger. Also, PTRS gives them some power vs vehicles, but only vs LVs. They are bretty bad vs mediums and heavies. Plus, when they get PTRS they drop significantly at AI. AT satchel is hard to use vs carefully playing opponent. If u take T1, you need to fast rush to T3 to get some reliable AT, or backtech to T2 if your resourse control is not enough, or else you wouldn't be able to counter tanks well.
I'd say penals are not overperforming, but overused. That's mostly because using cons is much more difficult. I thought about making penals something like osttruppen, it may make soviet infantry play more variative.
T-70 had a veery long sight range, but that is being fixed, let's hee how it works.
As for SU-85, it got a time loop when switching from focused fire to normal, and vice versa. The self-spotting is effective, but punishable, cause u can't run away fast. Su 85 has a bad time against raketens, cause it can't spot them in stealth. Maybe reducing the pen for vet0 and vet1 but keeping the vet2 pen is a good idea. But soviets still need good stock tank destroyer, cause they face better armored medium tanks, panthers, tigers and especially brummbars. Zis alone would not fulfill this role, and SU-76 has been nerfed already to not being able to fight heavies good.
Guards are strong, but expensive. And they are not the ultimate unit. They win against mainlines, lose vs ranged elites. Button ability is quite expensive, and is a waste of ammo if your enemy has vehicle smoke.
Seems to me that your argument (and mine too) are all questionable anddepends on the point of view. The problem is, as I think, that there is no common understanding in the community on how should each unit perform in ideal balance.