Google is resurgent, kicking butt and taking names. Their Panda machine learning allows them to see just how dirty our SEO rooms are and they have a Penguin for a cop.
Penguin and Panda mean those site heuristic such as Time On Site, Pages Viewed, Return Visitors and lower bounce rates become beyond important. The best way to tune those metrics is tell better stories and worry less about over optimizing your site for the old rules. The old rules are gone. This article discusses the new SEO rules and what they mean.