The IS2 has 340 armor and 1040 health, so that's not a good reason. Yes the is2 is slower, but it's mobility is still plenty good enough for a heavy and that protection is much more reliable
I'm only asking to give back 300 armor on Pershing, with 960 health. If it needs a slight mobility nerf that's fine, but I don't think it would need to be much
The panther is it's counter. You should compare it to the other 230 fuel heavies, which are all good against infantry as well. And the pershing really isn't that much better than them at AI anymore
I think nerfing the speed for 300 armor and adding the speed back through veterancy could work, I mean looking at its vet it has the lease bonuses out of all heavies price around it (no range, rotation or top speed for obvious reasons although I think it should get 5+ range).
Anyway, I would replace vet 2 crews defense since no one would really miss it. After playing around with it for a while, I cannot justify its cost and timing with what it brings.
Panther has higher acc/dcc and top speed than the pershing, it really dosnt help its case.