I used the _http_requests table in Postgres and created a Viz using Tableau Desktop with the following calculated field:
DATEDIFF('second', [created_at (_http_requests)], [completed_at])
I add the "worksheet" dimension, sorted by [Elapsed Time], and voila, a list of worksheets sorted by slow performance.
Here is the schema for the _http_requests table: Workgroups Database
Steve this is a great idea!! thanks for the tip!!.