Some interesting info Vanir, but a few details are incorrect.
The first point I may be misunderstanding you, but you suggest a D-0 wreck was found to have outboard 30mms. I think you may be thinking of the famous photo of a D-11 wreck showing outboard 30mms.
The second point is about the WGr21s. They did work, and were effective. At least, they were effective enough to be worth the weight and drag. They were also around a lot earlier than the R4Ms and used in wider numbers. Entire squadrons of Zerstorers would use them at once. They could push bombers around, but it wasn't a shock wave that was the real reason. The main intent was to hit the bomber to blow it apart... The secondary intent was to scare them psychologically, and force them to take evasives and thus break up the bomber formations. The WGr21s were available early in 1943, if not before then. The R4Ms were only available for limited use at the beginning of 1945. The reason R4Ms weren't used is because they were too late. The first R4M kills were in March 1945 when Me262s fired them against B-17 formations. WGr21s did the job until something better came along.
A slight edit: I think you're right about the WGr21 was not used on 190Ds, I'm not suggesting all the rest is inaccurate, just these two tiny details.