I agree that Proxy affinity has definitively been useful in fine-tuning repository access.
Currently we have around 24 Veeam Backup proxies across 12 host clusters, six locations and 3 vCenters.
Proxy affinity has helped ensure that the most appropriate resources are used for each site and environment plus we are better able to manage concurrent access.
However it hasn't helped with job administration, this is where proxy groups would be beneficial.
Rather than having to add/remove individual proxies from multiple jobs for backup, copy and guest processing, simply add or remove them from the group.
Would save our backup administrators a heap of time.
Microsoft, NetApp, Symantec, Veeam, Veritas and VMware certified professional
MCTS, MCSE, NCDA, NCIE-BR, ASC, SCS, VMTSP, VTS, VCP