You can but restore of a VM is not straight forward, especially if your VMWARE is using automatically load distribution, which makes the VM move from datastore to datastore
If you run backup with netbackup anyway, why not look at netbackups integration with vmware ?
I think that using NDMP won't recognize individual VM's on a datastore, won't perfrom their snapshots etc. NDMP is more suitable for traditional file-level volumes.
Here, I'd use Replication Director for VMware, which is aware of individual VM's and also aware of supported (SQL/Exchange) databases in them.
Refer to this topic in NetBackup77_RepDirector_Guide.pdf, chapter 13.