It has been nerfed too hard, I think pretty much all heavies besides the JT and IS2 (with preview mod buff) needs buffs. I don't mind the change to nerf the rear armor, but the front armor should be buffed to compensate.
To compensate for what?
Pro tip: overpowered things get nerfed to become balanced, not to be buffed again
heavy tanks were unkillable even after a perfect flank which is risky itself, their front armor has nothing to do with that, and what's more, it's balanced at this moment. Don't forget Relic wants to get rid of RNG, and high armor is constant dice rolls.