Update:
After a couple weeks of tinkering, I believe I have all the bugs worked out of my Sophos XG VM. I have been traveling for work lately (Oracle Consulting), so I haven't been able to fully dedicate a large chunk of time all at once.
My Ubiquiti APs are all running great on a separate VLAN, big shout out to DavidRa for then assistance.
I am running Sophos XG on the 4th node of my c6100, in Hyper-V. I added a 4 port Intel PT Network Card for my WAN, LAN and secondary ISCSI subnet my SAN traffic runs on. In addition I have SSO working with active directory, as well as SSL VPN . I just came back from being on the road this week and had a chance to test the VPN, and it's working perfectly after some tweaking with firewall settings.
I love the interface of Sophos XG, especially coming from OpenWRT. While the learning curve was a bit steep, now that it's running well, it's a breeze to manage.
Thanks to everyone who helped out over the past few weeks!