Can someone explain why Diana...

The recent Diana labeled guns aren't quite as high quality as the 100% German made RWS guns in fact Diana is having China produce many of their guns as well as sourcing cheaper German parts to build their guns as hybrids from parts made in various countries including China.

I agree as a prime example I can easily mention the Diana Storm rider which if you look at it is exactly identical to the artemis PR900W. at least appearance wise. Probably produced in the same company. 
 
If you look at the current Diana Catalog they clearly indicate which of their airguns are manufactured by Diana M&G in Germany. Essentially all of the higher end Dianas are still manufactured there. For the springers that is everything from the Model 280 on up.There is no longer any relationship between RWS and Diana. RWS is marketing clones of Diana models they have previously imported.

I have recently purchased a couple of months ago a Diana 280. The build quality, fit and finish is equivalent to my Diana 34 that is 15 years old. If you have any interest in a Diana then at least check out their catalog to find out about its specs and manufacture. It seems that there has been a lot of misinformation going around about the latest Dianas and where RWS fits into the picture.