I'm rushing off to class now, so this will be quick, but you might try reporting this to the stop_plagiarism comm. They handle cases from all fandoms. You should definitely report the plagiarism to the site managers, but the Stop Plagiarism comm is also good to have --someone takes on your case and approaches the plagiarist, and I think it's good for them to know that people (not just the author) are watching and taking this seriously.