The following SQL query will give you a total count of cases for each individual user in CRM 2016 since April 1st 2015. You can change the date range with the following line: WHERE ca.CreatedOn > ‘DATE HERE’
SELECT us.fullname, COUNT(*) as [Total Count] FROM SystemUserBase as us with (nolock) LEFT JOIN IncidentBase as ca on us.SystemUserId = ca.OwnerID WHERE ca.CreatedOn > '2015-04-01' GROUP BY us.Fullname ORDER BY [Total Count] desc