I rely on the recent activity block, but I don't feel I have the
problem you mention, because I frequently go back to the course main
page, and the list gets refreshed
I also don't have this problem myself 
- I know how the block works, so I always refresh the course homepage just before logging off. My concern is the students. I just think it should work intuitively, without me having to tell them to do the same. And I know that some of them forget to refresh the homepage anyway. 