Personally I find the balance between the P4, the T34/85 and the Easy-Eight a bit more interesting currently to be honest.
The balance between the Panzer IV and the Easy Eight is the real red zone. If the E8 is fine, the Panzer IV is under-performing, and vice-versa. There's just too much a leap in armour, accuracy, and penetration to be just 10 fuel apart. Between the Panzer IV and T-34/76 the Panzer IV has a major AI advantage and minor AT advantage.
___
T-34/76_
| Panzer IV
Max: 8.3271 | 13.4308
10m: 7.2955 | 12.2971
Min: 5.3594 | 05.8090
That's without upgrades, and nevermind the gun is slightly more accurate with slightly larger lethal AOE. Add in the roof turret and the DPS is 3x higher than the T-34/76 (though still spread across 4 weapons).
Regardless as I said, the problem isn't that the Panzer IV is weak (though personally I feel it lacks AT punch), the Easy Eight is hugely over-performing for it's price and making the Panzer IV look bad. Maybe slight Pen buff for the Panzer IV, but definitely a cost increase for the Easy Eight.