You asked why it has 286 armour.
It's because it exchanged higher armour for health to make it more survivable against tank destroyers.
The health is much more powerful than the armour. I don't see why you'd want to revert that.
previously, the when the panther was at 800hp, it got its extra HP at vet 2 to 960hp, it didn't get the free hp, it was merely taken from its vet 2, while having its armour go down. Before the panther changes, the old panther had better defensive stats then the new panther at vet 2.
Regarding OP's suggestion, i dont think these changes will do much and shouldn't be implemented, plus i think some TD's are going to be getting nerfed anyway (most likely jackon). Right now if panther does get a buff, it will most likely be in accuracy