As I've said, there seems to be some leeway in armor penetration. Personally, I want to see that removed, since it isn't crucial to the game play.
The M4A3(75) cannot penetrate the frontal armor of the tiger. Even at point blank range, you CAN'T get a hit I think. T-34/76 is a bit better, but its still unlikely that you'll suffer anything worse than a damaged pintil gun unless you are incredibly unlucky or incredibly stupid.
As to the Panzer and M4A3(76)W, they both should only be able to penetrate the frontal armor of the tiger at around 1500yds. Again, I would like to have some of the tigers invincibility status restored.