Hey,
Just a quick post as I'm still on vacation but have been made aware of my content appearing elsewhere. My D/A page is the only place that I have my series on, I don't have another D/A page and I'M NOT ON PATREON!!!
I'm not charging for my series or any other content, it'll always be free so anyone claiming to have extra content behind any kind of paywall, whether D/A or anywhere else is BS. I had a tantrum this morning and disabled the downloads on my new uploads but I've chilled out again now so I'll put them back on later today when I get a little free time haha.
Something to consider, and feel free to reject it, but there might be some value in establishing an official Patreon account and putting your content behind a paywall, even if you then give everyone free access and never actually expect anyone to pay for it.
Legally, you already own the copyright to your work, however, there's a practical difference between pursuing someone for redistributing content you've always given away for free and pursuing someone for selling content that you've established as having commercial value. In the second case, the pirate has a weaker potential fair-use argument.
There's also the practical consideration that Patreon might take a copyright complaint more seriously when the legitimate creator has an official account offering the same content behind a paywall, rather than when the content is exclusively available for free on DeviantArt. I don't know whether Patreon actually makes that distinction, but it seems plausible.