As a general rule, I tend to say that questions are often more valuable than answers. That's because some questions may be rhetorical, others may have no single right answer and need revisiting often, and that even in considering simpler questions with more straight-forward answers, that consideration may often inspire new insights or ideas. Questions open up our minds, where answers may sometimes blinker them.
is the content of the heavy landing pages relevant to the rest of the site? I feel confident saying yes, very relevant.
Remember that relevancy has to be more than just being on topic. Context and mind-set are just as important. You may need to further test that the people who were asking the questions that your content seeks to answer match the mindset you'd imagined and predicted.
For example, there was an informational site all about a particular subject matter that hoped to sell books on that subject. The logic of its creator was that people who were interested in his articles on the topic would be ideal customers for the books on the topic. The reality however was that people already knew where to buy books, and a large percentage of those going online for fast answers were not those really interested in the subject itself, just wanting a fast answer. A lot of students doing homework hit the site, copy pasted sections, and left. They had never had the interest in the topic, only in getting the answer for their homework as easily as possible without reading the textbooks they'd been given for free. The content was superbly relevant to the topic, but not to the mindset of deliberately not turning to books.
There are as many ways to test this as you can dream up, and then more that only others would dream up. Just bear in mind that the question itself, and how it opens your thinking up in asking it and seeking answers has value in itself. Think, invent, posit theories. Put in links that would appeal to other mindsets or motives and track clicks on those (using redirected links allows you to track 'hits' on the redirection script). Ask yourself "If these didn't have the mindset and intent I'd expected, what might they be intending? What might help those people and intents?"
Is the site so unappealing they don't peruse a second page? I suppose, but the length of stay on the 100 or so top pages seems long enough that that isn't the issue.
Obviously, if those times are based only on the 20% who don't bounce (which would be the norm of analytics) then those are highly questionable figures based on a small minority of your audience. Further, such a small sample is far more easily skewed by an even smaller proportion within that small sample, such that it could be that just a few people are leaving the tab open for very long periods while reading many articles, and the average of even the 20% minority without those is just a minute or two.
If I'm doing an awful job inviting further reading, how do I test that?
In part, by simply asking yourself the question and seeking your own answers. This is the value of questions that I speak of in my first lines of this reply.
Obviously, by being aware of the possibility, you'll be more conscious of what "Calls to action" to read more pages, or just learn more about the author, or see a clearer picture of figure 1, or whatever. And don't be afraid, for the purposes of both testing, and of providing the best experience, to even suggest reading elsewhere and other articles (using links you can track the clicks on).
Edited by Black_Knight, 28 March 2016 - 12:55 PM.