Currently SU-76's with it's penetration is surely no light tank (in my opinion), since it just beats down everything from range. It's no problem that it was buffed, but I think they overdone it, while the Stug-III is now just an ordinary tank destroyer, with simular stats as other TD's. Now Soviets have next to their ZiS and SU-85 also SU-76 (with Barrage) as 1 unit with barrages is not enough they just gave it 2 units to obliterate your AT and MG's. To play defensive mostly of the time you have to make a static frontline.
Well, SU-76 also doesn't cost like light armor. Its just 5 fuel short from medium tank destroyer M10.
It already have lower damage, hp and armor to warrant it light TD status and light TD is still TD.
On top of that, SU-76 barrage is highly inaccurate and have much longer cooldown then ZiS-3 barrage, its nice addition that always was there, but it was never something you could rely on, especially since if first shot won't wipe you, you can simply re position few meters to the side and be perfectly safe.
Also it amazes me that axis only players believe sov T3=ost T3.