Facepalm
Panzerfaust can penetrate 200mm @ 90 degrees
considering the velocity of the PF, which is under 50 meters per second, you have to arc it like a mortar shell, which means the orientation of the projectile when it hits the armor plate is going to be far less than the angle of the plate to the horizontal....you're going to get penetration virtually equal to the 90 degree penetration value of the faust (again, 200mm).
The frontal armor of an IS-2 is only 120mm at 60 degrees. Even if you hit the frontal plate at point blank with horizontal orientation, the Panzerfaust will easily penetrate in real life. The side armor is only 90mm at 15 degrees, which means the Panzerfaust will obliterate IS-2 with a side shot.
A Panzerfaust can penetrate the frontal armor of any tank in World War 2, with the exception of maybe super heavy tanks/destroyers like Jagdtiger, and destroy the crew in a single shot. The blast actually releases hot gases at 8000 meters per second in a concentrated area, which generally speaking tends to kill people.
So realistically the faust should kill any tank in Ost with one shot from any angle.