For those who may have also come across this issue with mounting SMB2.0/3.0 via cifs on SUSE 12 SP2, an install of SP3 didn't work.

What did work, is the new patch cluster SUSE released Jan 2018, that had the following packages:

cifs-utils-6.5-9.3.2.x86_64

kernel-default-4.4.103-92.56.1.x86_64

samba-4.4.2-38.14.1.x86_64
samba-client-32bit-4.4.2-38.14.1.x86_64
samba-client-4.4.2-38.14.1.x86_64
samba-libs-32bit-4.4.2-38.14.1.x86_64
samba-libs-4.4.2-38.14.1.x86_64
samba-winbind-32bit-4.4.2-38.14.1.x86_64
samba-winbind-4.4.2-38.14.1.x86_64

These updates were deployed to the server I had a problem with (that wouldn't mount samba 2.0), and after a reboot, magic, cifs mount for SMB2 working (no config changes).

I'm still running SUSE 12 SP2 enterprise. What ever magic was in the above packages, if fixed my problem. Thanks!