That is a very good question, of which I have not an answer. I am eager to hear other replies adding more help. Offering a query I ask how do you know you are being copied? I really do not go hunting to see until recenty, although maybe I should more.
I am empathetic of your feelings. There was a big scare thingy here a bit back when a new site was put up and they copied near everyone articles and not just one but many. Have you submitted information to Hubpages?
I really do not like plagiarism nor copyright infringement. Yet, technically other than the DMCA procedures not much can occur without damages occurring. That is a dilemma of tsmog my writing entity. That 'thief' would have to be making a pretty penny for a court to consider the complaint. Again, the procedure of following the procedure for a DMCA complaint can be found at the Learning Center, which may offer more hope https://hubpages.com/community/Learning-Center-Mod...
Sharing I wrestled with that dilemma once while another hubber shared maybe to consider it a compliment tsmog was copied or plagiarized. I pondered. Next, I sought how not to be copied or plagiarized on the web. I know that doesn't offer much regarding how it feels, believe me. I did a search on the book I am writing here at HubPages recently and I gulped then swallowed. My position is It would be easier to keep writing than offer pursuit, yet. The internet is pretty cool. They can track down the origin of content pretty swiftly sometimes.
So, for me to come out ahead the answer is to get it read by more than the 'thief' or just let it rock and roll until the 'thief' has a pretty penny and then pursue that 'thief' through the DMCA and the court system. Collect what is owned and due. The only element of consequence is time and a bit of research and track the 'thief' down. Kinda' like the old west days with a bounty hunter. Or, like 'Dog' does on his TV show.
I hope you discover something helpful with some this wandering of a bit and a byte, yet I offer a hug too. Not fair I say.