I think the Dev-files are for those who want to try developing content. Installing manually should get you all the files, but you should put in a ticket with their help desk. They might not be aware of the DIM not installing that content any longer. On the other hand, they have dropped most older V3 content. I for one just picked up a texture for V3 last week from another website.

The dust settled, thinking "what a fine home, at least for now" not realizing that doom would soon be coming in the form of a vacuum cleaner.