It would be disgustingly unbalanced in the endgame TBH =/
As an iLvl 340 healer with partial VIT melds I'm just below 37k with food. Raid buffed? I'm just shy of 40K and have room to surpass that if needed for Ultimate Coil.
So now we're talking a 6k oGCD barrier on the squishiest person on the party (going up to just shy of 11k on a warrior) with a 24 second cooldown. Not to mention that it'll completely ignore infirmity style debuffs and such.
The lily requirement is fluff, that would trivialise so much AoE stuff it's unreal. SE already got burned with fixed percentage based abilities via 2.x Lustrate. There's no way they will let this ability balloon out of control like we saw prior.