LostOne, I followed your link from another thread. I want to make sure I understand what you're seeing. It sounds like your post-Panda INBOUND traffic has held steady, but since you made these changes visitors just aren't viewing as many pages during their visits, even though they're staying longer.
If that's the case, I do think Tedster's theory could make sense - before, they were bouncing around to pages that weren't really what they wanted, and now navigation is much more clear so that's not happening. If so, that's mixed news - obviously going to hurt pageviews, but should build more visitor loyalty.
Your solution of putting "related links" at the bottom of the page text should help - did you try that? Another option would be to cross-link related pages from within your text.
Don't forget the spam detection patent, which could delay any benefits from changes you've made: [webmasterworld.com ] It can impose a time delay on the rankings reflecting your improvements.