Web analyst here. Those stats make About sound fantastic, as a matter of fact. There is no such thing as a universal "usability" metric, and everything is relative to the site and its goals and use cases. For About, those statistics are exactly what you would expect if the site is doing its job well.

The use case for About is you have a specific question, and you find a page that answers it. If the page actually answers your question (i.e., the site is doing its job), then you will have no need to view other pages, so your bounce rate will look high. If it answers the question succinctly and efficiently, your time spend on that page will be low. And if your problem is actually solved, you won't have to come back. And lo, that is actually what we see.

If About isn't doing its job, then there are two common "failure" scenarios. The first is they spend a bunch of time on the site, trying to find the info they're looking for. The second is that they exit the site and go back to Google. The first failure scenario has a higher "usability" score that the success scenario; the second failure scenario actually looks pretty much identical to the success scenario. Google could distinguish between the two by seeing whether users come back or not; you didn't provide that data, so I can't tell.

About.com is not a content site the same way as a news site or a blog. If you judge it by metrics suited for such a site, it will appear lacking. If you judge it by its own goal, it might actually be succeeding (but you need more data to tell for sure).