Sure they have, mines and AT guns are best counters to panther. Doesn't change the fact that panther spam was quite common for axis in the past and T4 recived only buffs since then. The main reason why people don't do it any more is the massive buff stug got.
No, I mean the Tank Destroyers Allies' got now which all reliably outrange and penetrate the Panther. Combined with what you mention, I'd say there's definitely no excuse to get rekt by Panther spam anymore.
StuG Gs probably are a wee bit too good though as another part of the equation, which no one really wants to touch while vet 3 double M1919A6s (heheheh just imagine the guns floating around and shooting with stars above them) will rekt the other obvious option of AT guns.