Feel free to close the task, we don't really need it that much. In 2006, DjVu support was added to MediaWiki. Now commons.wikimedia.org has about 278,000 DjVu files, so it's been pretty popular and successful. But the code in MediaWiki has not changed very much. We had a place in the database for type-specific metadata, and the original author simply dumped the complete output of djvutoxml into it. When we need page dimensions or text for search indexing, the media type handler is pulling up that...
I see that it's still not fixed, 14 years later. Maybe it's time to remove the comments I added to the MediaWiki source about djvudump being temporary.