VAAI for NFS is a specific feature for vCloud to talk directly to ESXi to initiate the VAAI commands as required. This is different than VAAI for VMFS based volumes. Please don't confuse the two, they work quite differently.
vCloud Director can use any VMFS/NFS based solution, generally speaking, but the VAAI integration varies with the two.
When you issue the 'Consolidate' feature, vCloud Director issues a 'Promote Virtual Disk' API call to vCenter. vCenter finds a host and passes the promote command down to an ESXi host to perform an action.
You can find more details here: Linked Virtual Machines - Look at the Promote section.
In this sense, vCloud Director is handing off the command to vCenter completely. So I would focus on the host performing the Consolidation (aka Promotion) and see what can be tuned at that level.
