On paper ! Panther and Pnzr IV literally the nightmare of RNG Street plus slow like an Excavator. If you cant literally deal any consistent damage Those "nice vet gains are" irrelevant. Its Nature of the Vehicles stats. Thats why It needs to be adjusted.
How can you describe them as "slow" when they have stock blitz skill to maneuver like crazy? Panther is one of the best dive-in tank in game.
And why you think they are the only units being challenged with RNG? It works the same to the allies tanks too. P4j has second to best AI in medium(sherman with HE being first), with exceptionally high armor(234) in medium class. You can force opponent to roll the dice when it comes to medium vs medium match.