It's great to see such an in-depth analysis on metrics. Another useful metric to consider is the trimmed mean. It may not be as detailed as histograms, but it still provides valuable insights and a clear regression signal. I wrote an article on measuring network service performance that tries to demonstrate the trimmed mean's ability to address percentile and average issues: https://medium.com/star-gazers/measuring-network-service-performance-fc987a794ba8#9653