After a game I had my full health vet0 croc run up against a vet2 stug and the stug killed it. Both penetrated most of the time, but the croc deals very negligible damage to tanks. It also shot the wrong target until I got right up to it. This wasn't an empirical test, but I don't have the time to recreate it in cheat mode. Also, more health means it will take more time to repair when it gets shot a whole bunch, and this too applies to other heavy tanks.
So 2 vetted TD killed a mostly AI tank...and the Problem is? Test the Croc vs a Panzer 4 which is actually a tank and not a TD.