...simply arguing that its ridiculous to only look at the gun stats when comparing the stug and su76 and ignoring that the su76 is THE glass cannon incapable of bouncing anything heavier than a scout car and being unable to take many hits either.
The SU 76 is a "glass cannon" that seldom gets hit by the hammer because it can stay out of range (gun stat)
Not that 140 armor on the StuG gives you that much of a chance, as even the mediums it is supposed to counter has a chance penetrate it like 80% of the time - but it gets into harms way more often as it does not have the 60 range the Su 76 has.
If anything is a glass cannon, its the StuG. It does not has the range to avoid being shot at, it does not have very meaningful armor either, but it packs DPS because it fires fast. It does not have however a clear role. Is it for supporting infantry? Counter light vehicles? Mediums? Heavies? In fact it does it all with varying efficiency, and like the Su 76, it can be even useful against prediums/heavies trough sheer ROF and fairly high Pen, which is the Panthers job (or at least should be, as its ill equipped to do that).
However along the same lines of the SU 76 should be re-balanced, so should be the StuG, as a dedicated light/medium tank killer. Its effective DPS against heavier vehicles should be lowered while maintained more or less against mediums, and probably it would be a good idea to push the slider a bit towards protection. Where all units have a chance of penetration, and most do just standard 160 damage, RoF is the king of DPS, and which is what makes spamming cheap, high RoF units cheese.
So IMO the good way to rebalance the StuG would be to decrease it's DPS, particularly against heavily armored units but increase its survivability. 50 range is OK for the StuG but it works poorly with the low armor values as the units (mediums) can fairly easily overwhelm it via brute force.
i.e. change the StuG as follows
15 % reduction of Rate of Fire
15 % reduction of Penetration
30 % increase of armor (i.e. same level as Pz IV) to compensate
This would reduce the StuG DPS by 30% against heavies (pretty heavy nerf), 15% against mediums and TDs (slight nerf, but its less spam-desirable), but would increase its survivability against light and medium vehicles, unless they flank it. Overall a less cheese unit with a clearly defined role.
P.S. Personally I would love to see some damage increase against units in trenches/buildings/bunkers etc., to give it a bit of historical flavour.