Do you think analytics metrics such as 'time on page' is playing a more vital role in keyword selection versus just high-traffic volume?

Yes, time on page shows user engagement. Because search engine ranking factors change monthly, your website might not be ranking for your target keywords per se, but time on page proves the user likes what they are reading. 

Time on page is a tricky metric because if you have a standard implementation of any Web analytics tool, then they don’t provide you the time on page for visits with single-page views.

So, it is not that these metrics by themselves are playing a more vital role, because while they are great diagnostic metrics (at least bounce rates), they are simply not strategic enough.