I agree that tactics and training were far more important, though I´d also caution that later on the advantage in that regard against the Soviets was smaller than during Barbarossa and Typhoon. And I made in an earlier thread the rough calculation that by foregoing production of both Tiger and Panther they could at most field in their place twice their number in T34 copies instead. And that was the high number which made some rather optimistic assumptions about resources, industrial organisation and manpower available. Now by concentrating on the Pz IV, an established model the chances to achieve that rise, but they would still face 4:1 odds just against the T34s produced alone. If they were able to concentrate all these tanks on the Eastern Fronts that is. And not mentioning other tank models used there. Pretty harsh demands on a tank that is about equal to its main opponents.I realize that I am in the minority here, but I just do not buy the argument about needing to have technical superiority. What made the Panzer divisions so formidable was not their equipment but their tactics and training, plus the specific decision to equip all tanks with radios. As I said earlier, remember all those times during Barbarossa and Typhoon when obsolete Panzer Is and IIs repeatedly defeated far better Soviet tanks long after the surprise wore off.
If they already wait until 44, then why should they introduce at that point a tank which clearly is maxed out in its armament, instead of an improved version of the larger MAN tank, where otl it is proven that it would have had growth potential. It would have been possible to upgrade that one with an 88mm gun in the future. Meanwhile while the Pz IV with Kwk42 failed ultimately due to weight issues, it also had some other issues, namely crew space in the turret, which would not have been better in the DB modell, since it had the same turret ring diameter. And the diameter can´t be increased without changing the hull.To your specific points, I don't know if you read through this whole thread, but in the scenario that we worked out the Germans are willing to wait until 1944 to introduce this tank, meaning that they do have time to do the completely new turret.
With a longer design stage the reliability issues in the MAN would probably have been adressed before fielding it. It is of course possible that the DB would have addressed its water problem as well, so with a delayed introduction neither does matter all that much. But at the point the decision was made otl it is imo understandable to want a tank that could ford a river.Regarding water bodies, that's unfortunate, but even if true its still better than a vehicle that spontaneously breaks down three-fourths of the time like the early model Panthers did.
In your delayed introduction reliability both can only be solved fully by changing the suspension, but it is unlikely in the middle of a war. OTL the Panthers reliability did improve, even with the same suspension. The stability disadvantage of the leaf suspension is inherent in the design though.As for the less stable platform, you admit that this would be outweighed by better reliability.
I made the comparison from the point the decision was made otl, at which moment the advantage to the PzIV was far smaller. And while the further development could have changed that, a longer development would also have helped the MAN design and that from a better starting point.As for being only a moderate improvement over the Panzer IV, this tank would have the exact same optics and same gun as OTL Panther, meaning that it would be able to penetrate a T-34-85 from 2000m, while the reverse would be the case from several hundred meters. That is a big margin of superiority, far bigger than that of the Panzer IV/48.
You also did not address the issue of the operational range. The petrol engine was necessary for good reasons and with it the DB design had a range not all that much better than the Tiger, which is damn pitiful for a medium tank. Barring a breakthrough in engine technology that did not happen otl there is no choice but expanding the hull for larger fuel tanks to address that problem.
To sum it up the main drawbacks of the DB version can only be solved by enlarging the hull (though they could limit the need to enlarge it by accepting that the tank can´t be upgunned further), which would increase the weight, just like the new turret with the larger gun never tested otl. Now who is to say what 5-10 tons more will do to the better power to weight ratio and the reliability which were the main advantages to the MAN? While MAN will have solved some of their issues and still have plenty room for upgrades.