I would think placing a call to action in the article (shares, comments, etc..) and then measure views against taking the requested actions, actions not related to CTA (are people sharing, liking, commenting outside the specific CTA), duration of pageview against a reasonable measure (i.e. how long would it take a reasonable person to read it and complete the CTA), negative vs positive responses (dislike on YT, negative comments on blog), performance (views, duration, CTA metrics) versus other posts both on your own website and competitors. Those are just some thoughts - to an extent it would depend on the content and the audience but I would set up metrics with goals before the article launched and then track against goals. AA review would help me identify improvements for subsequent articles.