One of Sleuth's most popular ways to track change failure rate and MTTR is by tracking your teams incidents. We have a number of wonderful first-class integrations. However, many teams have a home-grown or manual process.
For all of you, Sleuth now supports Custom Incident tracking! Just create a custom incident impact source and hit Sleuth's REST API at the start and end of an incident and Sleuth will do the rest, surfacing your blended change failure rate and MTTR.