what user rights does IDERA need on the instance, to be able to monitor an instance using DIagnostic Manager?
The SQLDM services (specifically the SQLdm Collection Service) are used to collect diagnostic data from the monitored instances, which is then displayed in the SQLDM Desktop Client and the SQLDM Web Console. The SQLdm Collection Service needs to be running under an account which has sysadmin rights on the monitored instances. This is documented at http://wiki.idera.com/display/SQLDM/SQL+Diagnostic+Manager+requirements under the SQL Diagnostic Manager Services section. The alternative to this would be to modify the properties of the monitored instance to connect to the instance using a SQL Server account that also has sysadmin rights. You can do this within the SQLDM Desktop Client by right-clicking on the monitored instance name and selecting Properties, then updating the credentials that are to be used when collecting data on the General tab.The user that is launching the SQLDM Desktop Client or the SQLDM Web Console does not need explicit rights to the monitored instance as the data collection is performed by the SQLdm Collection Service.
I hope that information helps!