... Suffiecient recon with flares etc will keep SU76s from harms way most of the time....
To make things even worse Flare are not essential since the vet 1 ability "tracking" increases sight so that one can see targets or do not suffer FOW penalty and the mini map information allows to avoid rakketen or barrages packs from out side their range.
Their range needs to come down to normal tank destroyer levels (pretty much all TDs have 50 range except the SU-76 which for some reason has 60) and their penetration needs to come down such that they're less effective than their weight in SU-85s versus a heavy tank.
That is incorrect. SU-85, FF, M36, JP 4 and Su-76 all have a range of 60.