I can confirm that DWR Support has been removed as of Jive 8.X. You will need to refactor your plugin code to remove the DWR dependancies.
Yeah, we noticed that too.. it's a lot better now that Jive refactored theirs to REST services.. like the opensearch API, which is accessible like this; /__services/v2/rest/openSearch/ENGINE_ID?q=SOMETHING
And we also changed our DWR objects to rest services which were there in our old customizations. And we successfully upgraded to Jive8.0.1 couple of months ago. ☺
Thanks & Regards