It is possible to block your videos from appearing at xvideos, follow the steps described below:
1. Contact them through this form:
http://support.xvideos.com/takedown/
submit all infringing links that you have found, and add that you want those videos fingerprinted. They'll take them down and fingerprint them, which will block those particular clips from ever appearing again.
2. If you know who's posting your vids, contact them using the same contact form:
http://support.xvideos.com/takedown/
at the bottom there's the box where you can describe that repeat offender - they usually add new watermarks to your videos that's how you can single them out. If there's enough evidence of repeat infringing (provide enough description so they can make sure), xvideos will ban that account or at least warn the uploader to leave you alone.
3. Contact them to fingerprint your whole content library:
http://info.xvideos.com/content/contact/
Submit your member zone URL and username/password to they can access it. They'll harvest all videos and add them to their DFP library. That will stop next to 100% of infringment cold, but it will not happen overnight, that work takes time to complete, up to several months.
They'll NOT start posting your videos left and right, so you can submit u/p to them safely. I was a bit uncomfortable with that at first, but in the end it all worked as planned - our whole content library was fingerprinted, and we were seeing LESS of our clips posted at xvideos every day, not more.
4. Make sure your videos have HUGE visible logo - if your older videos do not have it, add it to at least your newest ones. When they know you, and familiar with your logo, they will not let upload of your video through even if it escapes fingerprinting (for example if that is your most recent update that wasn't fingerprinted yet).
5. When they're finished fingerprinting, contact them to scan their whole library and remove all clips that were posted previously. In theory they'll do it anyway, but in practice it wouldn't hurt to remind.
With the help of what is described above, it is more than possible to get rid of infringment at xvideos almost completely. It will take some of your time, but it is very well worth it, since they're the biggest adult tube around - alot of lesser tubes are scraping them for updates, and you can take care of those too with one blow.
You can also try their "channels" system to promote your site. When you're not competing with your own uncut videos uploaded by some sick fuck the same day, it may work.