I have this generic versioned geodatabase question i.e.Which Geodatabase version is holding how many UNPOSTED outstanding Edits ?, which may be crucial to identify the query performance bottleneck in any versioned enterprise geodatabase having large number of editors. I have posted this query multiple times including Esri support however could not get satisfactory resolution. Version for ArcSDE10.2.2 to 10.4
Have you tried using the Version Differences tool in ArcMap, see http://desktop.arcgis.com/en/arcmap/latest/extensions/data-reviewer/comparing-geodatabase-versions.htm. This gives you information on the outstanding Adds, Deletes, and Modifies between versions.
Granted, you would need to do this on a version by version basis, but this may give you the answer you are looking for.
You could also use ArcObjects to create a tool that goes through all versions and gets a count of the differences using the IVersionedWorkspace, IVersionedTable, and IDifferenceCursor interfaces. See How to identify Unposted/Outstanding (A&D) edits of a version in Enterprise SDE Database using SQL interface? for more details.