You're absolutely right that there is not much content on that page exclusive of navigation, but in its defense the whole point of the page is navigation :) And it is just one page out of hundreds of thousands of pages on the site, many of which do have a lot of content.
I like your point about leaf nodes. Many of the domains that rank now either have a small # of pages total, or are extremely large brands with a lot of "trust", however Google defines it. In fact, these factors seem to outweigh having any original or useful content on the page itself in many cases (see post below).
If the problem is about too many leaf nodes, then cutting down "thin" content nodes (pages with little content, photo pages, etc) should have a positive effect. We've done a lot of this, so it will be interesting to see if that is the case.