Which is why we're talking about buffing the pen on JP4?
I dont think the stug needs it though, its not meant to be that effective against heavies
I'm not sure you need to if you tone down some of these stupidly high armour values. You could probably bring the penetration of the allied TDs down instead.
As for the StuG, it's a dedicated tank destroyer. Should it be less effective than the Panzer IV and Puma? Because against a 375/140 armour unit, it is.
Casemates can't circlestrafe.