The best practices are to put SAS WORK and SAS UTILLOC on internal SSD drives to you SAS Grid compute nodes. You would use a local file system.
As I stated in another blog post you have done, Solaris QFS can be used for the shared file system with SAS Grid on Solaris. We have not done any testing recently with this shared file system, but it did work in the past. There was no specific tunings that had to be done.
If you are having issues with this shared file system, then you need to work with Oracle/Solaris support to determine what the issue is.
Margaret