Change effective on 20 June 2018
The Application Metrics tab is now available for users who have the View permission on an application. It was previously limited to users who had the Operate permission. This will allow all members of your application to help diagnose and debug your application using the observations recorded from your dynos.
Configuration of Threshold Alerting, which is done through the Metrics tab, is still restricted to users with the Operate permission.
For more information on permissions, check the App Permissions dev center article.