Diagnosing and reporting operational issues to optimise system usage and performance is challenging on large-scale HPC systems due to their sheer complexity. At the Jülich Supercomputing Centre (JSC), we address this challenge with LLview, an open-source system and job reporting framework. LLview provides near real-time metrics for analysis through a web portal with role-based access for users, administrators, and support staff. In this paper, we present a series of use cases demonstrating how LLview enables efficient diagnosis and resolution of system and application issues, enhancing both reactive and proactive support for HPC users.