Raw devices OK on NFS from well known Vendor like NetApp.
But be aware that NFS file system writes can get serialized under OS control. And this can pose severe challenge.
Use them for tempdb's too.
I had an assignment where tempdb on NFS mounted files choked the server when tempdb cache reached certain level and had to flush the data to disk. Writes became serialized holding up all CPUs.
If you did nothing and let things run it would be OK after some time like 30 minutes or so. Server would be unresponsive to users during that time.
After isolating this pattern I could make the server in a sandbox environment unresponsive in almost predictable way.
With a case with OS vendor and SAP/Sybase the tempdb devices were re-configured as raw devices. And things started working OK.
HTH
Avinash