There's always room for improvement. Concentrating forces at the point of attack is something I'm not doing enough of, but I've played against opponents who use reserves heavily and have no problem putting the entire front, north to south, into reserve mode. You need troops next to those front line units or there are reserves everywhere. However, even Michaelt has commented that he mules for a reason and without mules, it's extremely difficult for the Germans to make enough progress, so I'm not convinced it's entirely tactics on my part. Plus there's too many other players, many of them quite experienced, saying the same thing.
Here's what I see as the challenge for the Germans:
On turns 4-11, before the Soviets have enough troops to carpet and fortify accross the map, the Germans need to be able to create salients that force the Soviets to stretch their lines. These salients provide encirclement opportunities, breakouts that can capture production or force Soviet pull backs accross the theater of operations. The Soviets (and I've played as Soviets and did the same thing) start creating checkboards every two to three hexes starting around turn 3-4, 2 to 3 layers deep in the north. Based on where the panzers are in a theater, you can go with 2 deep checkboards every 2-3 hexes at the extremities and 3 deep every 2 hexes at the main axis of attack. Soviet brigades can be used in later turns to fill the gaps of the checkerboard. Checkerboards continue until there's enough troops to start forming carpets. In the south, I see Soviets run back to the Denpr and pull back and form brigade/small division checkerboards using the logistical dead zone to prevent much in the way of advance as the rail heads are way back until turns 10-11. This is assuming the use of air transport to refuel heavily in AGC and AGS.
Here's where the combat mechanics make this defense difficult to beat. 1) You can only hasty attack from a single hex. Hasty vs. deliberate is simply a reflection of the time to take a hex, with hasty being a fast rate of attack, with higher losses potentially, and deliberate being a slower rate, maximizing casualties and minimizing losses. There's no reason why you can't hasty from 2 or more hexes, but because you can't, a hasty attack from a single hex against a double or triple stacked Soviet hex in good terrain is a crapshoot at best because the CV swings around wildly, even using one or two corp as offensive reserves. 2) So the safe way to attack is to use deliberates, but because FOW is pretty extreme, it's quite easy to get 80-1 odds on a deliberate, which should become an overrun costing 2 MPs vs the 6 or 16 MP cost. But because there is no overrun, it becomes a slow rate of advance, even with concentrated infantry, and the Soviets continue to get stronger and then start forming their carpets. 3) Once the Soviet brigades start arriving they can fill gaps, which take up ZOC costs for German movement, attrition, MPs to attack and hasty is dangerous because you never quite know what's in a hex even moving next to it.
So the combo of no overrun, hasty attack limitations and brigade level ZOC creates issues that prevent a good rate of advance and then the checkerboard becomes a fortified carpet, the same combat issues above still exist, the entire carpet is pretty much in reserve mode and the offensive comes to halt. The games stops being competitive.
This is why some Germans mule. Having 45 MPs in your panzer groups enable multiple deliberates that can clear out 2-3 layer deep checkerboards and open opportunities. The MPs overcome the combat limitations.
Any German players believe I'm off base here, please let me know.