Enable Activity Monitor for managed instance
The lack of activity monitor and/or via an applet in the portal to see utilization of the pricing level would be most helpful, not just for determining if we need to up size to a higher vcore model but to understand the load on the box by more than just what spid is active (cpu, disk, memory, etc)
Monitoring solutions available for Managed Instance are summarized in this article: http://aka.ms/mi-monitoring
Ian Bennett commented
Azure SQL Analytics is like Perfmon. Sure it can give you a lot of info but what do you see on everyone's desktop? - Task Manager, because it gives you the main information you need with 2 clicks - not 2 weeks of training, configuration and analysis. Handy, easy to use management tools have played an important part in the success of SQL Server and it is sad to see them being devalued by MS.