The SU76 may very well be batshit OP atm. That's probably not because of its accuracy though; it has the same accuracy as the Stug.
...
Having the same accuracy but 20% more range means that is actually 20% more accurate...
The chance to hit of all 60+ range TDs need to go down weather that mean lowering accuracy or size or both.
Imo TD should have around 90% chance to score a "natural" hit at range 60+ vs a Supper heavy and around 50-60 vs a medium tank.