So apparently there are a few known bugs with SMB in Mac OS Sierra.
One is documented here:
https://dpron.com/os-x-10-11-5-slow-smb/
I applied this fix and am still experiencing dreadfully slow performance when the finder tries to list the contents of any folder over SMB. SMB works fine on my 10.11.x clients and AFP works fine on my Sierra clients. Are others finding this as well?
