The Main gun of the SU-100(100mm D-10 tank gun)was a Little bit more powerful than the Panthers gun but weaker than the much longer main gun of the King Tiger/Jagdpanther/Elephant. So i dont believe that the SU-100 would easily kill all german heavys.
http://en.wikipedia.org/wiki/D-10_tank_gun
Yes it would kill all german heavies, because it could do that in real life, and in coh logic, all tank destroyers are completely innefective againts infantry but super good againts tanks.
Even then, the D-10T was just slightly less effective in penetration than the KWK 43/L71
The elephant has 400 penetration, KT has something like 240. Even tho they use the same gun IRL, their gun stats in coh 2 are completely differently due to the elephant being a TD and KT just being an all round heavy tank by purpose.
So an SU-100 would also probaly have huge penetration because of it's TD role, and considering it's penetration and range was superior to that of the ISU-152, in game the penetration would probaly be something like 350 or so and it would have maybe 70 range, same as ISU or elephant.
And please don't add the su-100. We don't need more bullshit super range super tanks