Losing a p4to the equally fast but 50% higher ranged guaranteed to pen TD is much more reasonable.
Why is the Jackson supposed to guaranteed counter the p4 even on defense, even if caught out of position, even if flanked but EVERY SINGLE other TD in the game isn't supposed to survive let alone possibly win getting caught out? The answer is because the Jackson is over performing and poorly designed.
Try to dive an equivalently wounded Panther with a sherman and let me know. Pz4 are also doing just fine overextending once vet1 and blitz activated, even get a second panic button with doctrine if required.
I'm not saying Jackson isn't OP, but what you expose here isn't really what makes it OP. What makes it OP is the need to fulfill 2 roles, countering medium tanks and countering heavy tanks.
We'd all love to have a solution to make it more dedicated to one or the other role but that's not possible until Relic move on and bring a solution on USF roaster.