Sorry, I wasn't totally sure about the ratio thing. It's just hard to say since the stats don't tell you where your views are coming (or not coming) from. I get that your point was the overall views have dropped though.
You could be getting users subbing due to the bandwagon effect. They just assume your series is good because you have thousands of subscribers, but then they never bother actually reading it. I imagine this would only get worse as your following grows. Seriously though, a lot of people subscribe to far more series than they could ever possibly read. That is totally out of your control and unfortunately, I don't think there's anything you can do about it. As @CyndiFoster mentioned, it also easily could be random people that sub then never come back to the site.