It's easy to latch onto the idea that stolen content is the reason for traffic loss because it's simple and is kind of logical, but it very rarely is the reason.
At the moment it is NOT the reason for traffic losses on Hubpages. Traffic is not being redirected.
There is A LOT going on with Hubpages and Google right now and I'm sorry to say it's complex - there isn't a simple answer. Traffic may take months to return, or weeks, or might never get back to previous levels. There may be things down the line that you can do to improve your pages so that Google likes them better, there may not be. This is the downside of putting content on a website that you don't own and don't have any control over.
It is still important to deal with your copyright though (and you can be assured that HP deal with their copyright too). Who are you sending DMCA's too? The hosting company? Google search? Google Adsense? Are you using the correct format? Sending to the hosting company is usually the quickest way to get rid of copied pages.