OSTHEER IS DONE WHEN IT'S DONE!
Come on, we feel guilty enough about having to include the Panther! There's no creativity or challenge invlolved in copy-pasting the Panzer IV as well.
and besides, the Ostheer isn't there to single-handedly represent the real German army in the East, but rather complement the existing Wehrmacht and Panzer Elite units and playstyle with new and interesting units and playstyle.
The problem is that there really is no equivalent to the Panther or the Tiger, so we have no choice but to include them. The Panzer 4 had a very similar role to the Panzer 3, and besides, the Ostheer isn't there to single-handedly represent the real German army in the East, but rather complement the existing Wehrmacht and Panzer Elite units and playstyle with new and interesting units and playstyle.