Sampling based on traffic is not a reliable measure of your website performance from an end user perspective.
Sampling seems ideal only when your application's environment is constant, which is why Sampling is a prominent feature in our Application Monitoring Service (APM-Insight).
However, In Real User Monitoring each end user's environment varies. Events to your website can be triggered by any user, from any location, by any browser or device, through any ISP as a result of any transaction.
Extracting only a sample might result in the metrics being on any extreme on your performance spectrum.
Our Snapshots(Session traces) are a result of sampling based on your apdex threshold as done by other products in the same domain.
We would like to know if you have any use cases or problems that sampling of pageviews would solve.