not2easy - 6:06 pm on Nov 14, 2012 (gmt 0)

If you are still publishing entire posts to RSS without using any tools to modify the content and track it back to your site I don't know that a DMCA with the host will resolve your problem. All they have to do is find a new host. I would take that step after addressing the things on your site that allow them to do what they are doing.

Publish snippets to RSS, not complete posts or pages.
Look at simple plugins that let you add a header, footer, backlink in every RSS item. As long as you are an easy target, someone will be out there looking at how to use your work to get ahead.