Kevin makes some valid points...as does duffsmom. It's easy to get traffic, starting a controversial topic will also get a lot of feedback (not all complimentary) and a captivating titile will draw people in...but good writing has nothing to do with any of those.
A fantastically well written hub on a boring topic will not draw comments. For example.
Not sure about the hubpage duration tool however I love google analytics...you can see where your traffic is coming from, where it goes when after reading your hub (if readers exit or look at your profile/other hubs), how long they spend in each hub, loyalty of visitors (if they are repeat offenders or 1st time visitors) and heaps of other interesting reports.
If you haven't already, you need a google account - sign up for analytics (it's free). It's a matter of copying/pasting your unique number (ie UA-12345678-9) into the analytics box in your account at the bottom of your affiliate settings.