the SU-76s biggest flaw imho is not the lack of the turret or the paper armor but rather the inaccuracy... its speed and range compensate for the lack of turret and the paper thing armor...
but the lack of accuracy renders its gun nearly useless at long range... and vulnerable at close range... and a properly supported SU-76 is gonna have trouble hitting the panzer 4 even with an AT nade... at which point it becomes redundant... too inaccurate to hit anything... too expensive a barrage ability... tries to be a jack of all trades... but fails badly...
I get your point, I did not know that the accuracy became worse after the patch (haven't played Sovs for a while now), but imo the pen and accuracy was extremely good before as well.
The thing is that it has to be bad in some way. It perfectly counters Light Vehicles like 222s. 251s, Flak HTs and Luchses by killing them or at least forcing them to move out of an area. The barrage then is just a nice bonus. It being free was a problem in the first place.
If you want to get a sniper tank hunter, you get the SU85 (which also has its flaws, but still).
The barrage is just extra And to be honest, I wouldn't be that bothered if they removed it entirely even without compensating buffs
I think all the "niche tanks" need this kind of "cheese" ability besides their main gun damage in order to be able to add a surprise element. StuG will make you inmaneuverable for a while. Puma does as well (?). AEC also has its thread shot. The Valentine can watch your enemy while sucking ass.