If Divine Benison could only be used with Lilies but still were oGCD, you'd never use the Afflatus heals outside of downtime. It would help with fights where you need to heal so little that you'll overcap lilies if you don't overheal and lose DPS, but they would make it so it doesn't generate a blood lily. I'd rather have it stay a simple oGCD like it's now and make something else to use with lilies you don't need. Something that doesn't invalidate the Afflatus heals, so not just a DPS spell or so. I'm not sure what would be good for this, I only know what I wouldn't want. ;D

If something increases DPS, most players will use it no matter the situation and delegate the healing, even if needed, to someone else. This is why Misery is good. As long as one Afflatus heal is really needed or during downtime, the other two are no DPS loss and you are free to use them (for healing or movement - preferably both).