I am not here to protect the tubes, but I presume and believe piracy on tubes is decreasing. The big tubes have content partnership programs for affiliate sites. And sites like xHamster now have enormous user base - isn't this all they ever wanted?
It looks like they did all the damage in the past and now they are trying to play nice.
The only answer I know is, what are top porn tubes sites:
http://mypornbookmarks.com/#Best-Porn-Tube-Sites