Lean metrics
In sequential process (Kanban), we aim to accelerate transition of the requirement from start to finish of the technological chain. In this case, the main metric of the process is your team's performance. It can be measured with the average number of hours required for the requirement implementation. The less this value is, the more efficiently works your process, and the higher is your team's performance. This value is called average cycle duration.
To analyze the more detailed information (how much time the requirement (or task) spent on each stage of technological process), you can use Lifecycle tab on the view or edit form of the task/issue. "Details of cycle duration” report can be used to analyze duration of stages for a suite of issues or user stories.