I just picked up "The Arms of Krupp," which hopefully should be helpful on some of my points.
On the topic of V-weapons, I see it this way: they cost a ton, and it actually took quite a few men to launch each one. If, instead of building missiles that may or may not actually make it across the channel and hurt someone, they had built, say, tanks or heavy artillery, then trained the men who would have been tasked with launching rockets to operate said equipment; there would most certainly have been a greater return, as far as tangible results go.
As an aside, (which I also plan to bring up elsewhere,) the Me-262 was through its testing and ready for production by mid-43, but since members of the high command thought they were still winning the war just fine with what they had; jet production was put on hold until 44. They didn't actually see significant use until very late in 44, by which point there were still too few jets to deter Allied strategic bombing.
Another great waste was the proliferation of armored fighting vehicles: Late model panzer IV was perfectly capable of dealing with T-34, as were Panther and Tiger I. Panzer IV's armour wasn't astonishing, but it was faster and more reliable than its larger brethren. I'd go so far as to say that if the Germans had focused on building either the Panzer IV or a fixed Panther as the main medium tank, with Tiger I's as a supplementary heavy, they could have cranked out far more vehicles than they did, simply by virtue of standardization. The monstrosities known as Tiger II and Jagdtiger may have had semi-impenetrable frontal armor; but they were heavy, slow, and maneuvered poorly. They may have scared the **** out of the people they faced, but they were too costly and time-consuming to make en-masse; and furthermore the vehicles themselves were too slow to push forward and take initiative during a counterattack.
Maus and Landkreuser... those two.... well, lucky for the Germans they never made it to the front.