Nocturnal Sect, hands down.

Short of the few level 50+ fights where people do not take damage often or there's lots of mobs showing up that you don't to grab aggro from (Pharos Sirius 1st boss), it's often not worth the use simply because you're not healing faster than the damage is coming in, and there's no way to further mitigate damage outside of those small shields like there is for SCH. I rarely if ever use this stance, no point when Diurnal can heal up everything as fast as a WHM can. And it hurts me to say that because I main SCH as my healer, I know how powerful those shields can be, but there's nothing to help back them up.