If I understood correctly, the data to detect the anomalies in the task run duration already exists, as shown in the table below, but you would like to see this as e.g. a bar chart or some other easier to consume visualization?
If so, I think you could build a dashboard starting with this query
https://github.com/PrefectHQ/ui/blob/master/src/graphql/FlowRun/table-task-runs.gql
If this is really important for you, you could give it a shot and contribute a PR to the UI repo or submit a feature request (even though I believe most new feature requests would now be considered to be added to Orion). I believe what you try to do would be much easier to show in the UI in Orion with
filters