NIOC may be needed when there is contention for different types of traffic on the same Physical Uplink. For example if Management traffic and Edge, Vxlan VTEP , Vmotion or other traffic types use the same uplinks. Generally may be good idea to keep seperate, but if not possible then Port groups may be designed according to traffic usage. So NIOC for a well designed uplink teaming policies that does not produce saturation, NIOC will just add complication to the design and configuration. NSX adds VTEP type of traffic, so general NIOC guidelines without NSX should be valid here.
On the Reference Design Guide QoS is mentioned for Robust Physical Network, but NIOC not referred:
https://www.vmware.com/files/pdf/products/nsx/vmw-nsx-network-virtualization-design-guide.pdf
The following design NIOC is used (This designs use Cisco N7K switches and UCS servers).
https://www.vmware.com/files/pdf/products/nsx/vmware-nsx-on-cisco-n7kucs-design-guide.pdf
http://blog.igics.com/2015/12/end-to-end-qos-solution-for-vmware.html
Although not a must, If there are different Tenants or Projects or Environments (Test, Development, Production), then Edge Gateway for each of them may be a good idea as there may be IP Overlap and different requirements for common Network services. Though one tradeoff may be the resource usage of these Edges, but theoritically there can be 2000 Edge devices per NSX Manager:
https://www.vmguru.com/2015/03/vmware-nsx-v-configuration-maximums/