Agree with not2easy.
The DMCA request is not really designed to say, "Hey Google. Stop ranking this guy who has copied my content higher than me."
The DMCA is a takedown request (or at least every that I have used it). It's really designed to say, "To whom it may concern. This guy is violating my copyright by publishing my content without my permission and you party to that infringement by hosting their content. And I want it taken down."
But it's not really going to help if you continue to allow them to suck your content out of your site so that they can mash it up on their site. Chances are that it could reappear again on the same site at a different URL.
Personally, I've never been a fan of RSS and syndicating my hard work so that others can profit from it (just like this case).