In our experience, it's the low eCPM that tends to drag down the whole site. It's not necessarily the fault of the page or even the inventory of advertisers, it's what they are willing to pay and whether your visitors click. You could have the most popular page on the web about, say, inexpensive ball point pens, and there may be plenty of office supply outfits and gold and jewel encrusted ball point pen sellers bidding high on the keywords, but their click through could be near zero, ergo lousy eCPM. There may also be some genuine cheap ball point pen sellers, but how much can they bid on an ad? Even if their click through is good, you'll still have a low eCPM.
Whatever caused the page to be a low earner, in the experience of many of the publishers on this forum, you'll earn more in the long run if you remove Adsense from it. It's kind of surpising that the Adsense algo can't figure all this out and keep the earnings maximized for everybody, but it must be following some rules that get in each others way. My guess is that like many code monsters, the creators aren't sure exactly how it functions anymore, they just try to tweak it for the best overall results.