I'm seeing a different issue in my micro niche. Sites with new content on home page seem to be doing better since 5/1.
Also one 250 page site with only 10 on topic external back-links to the page that is ranking for our top 2 word term. Internal link structure or site ranking seems to be pulling them up to similar levels to pages with hundreds of on-topic external back-links.
Both of these things are too easy to spam to last.
PS Having said that I may add some fresh content and focus my internal back-links. It can't really do any harm.