There is a free tool in the
XrmToolbox called "FetchXml / View Record Counter" that you can point at a view and it will count the records in the view. It does this by returning all the rows, 5000 at a time.
I have also built two commercial add-on products that run any FetchXml aggregate on any number of records (without returning all the rows). One works inside CRM via a managed solution and the other works via the command line. They're currently in beta.
If you're interested in more info, please contact me here:
https://www.xrmedge.com/home/contact/
Regards,
Aron