I had given up on KVM completely and ditched the entire HA project for many months. Things changed and I finally got the old box out of the closet and fired it up, this time running CentOS 7. Again, ran into the aforementioned issues with UEFI boot. The solution is documented here: Can't boot hassos? (x86_64 KVM VM) - #7 by q500dude
The EDK2 firmware is required to boot the qcow2 image provided.