8 second cooldown
Consumes the target's Power Word: Shield effect, healing up to 5 injured targets within 40 yards for the remaining absorption amount, split between targets.
Numbers could be adjusted, of course, but think of it as a cross between Circle of Healing and Swiftmend (because of the PW:S requirement). It would scale with mastery because it's based off of the remaining shield absorption, but it wouldn't be an absorb effect, which I think is important because Disc's problem is that absorbs are too good compared to regular heals. You could either pop an existing shield for lower healing if you need it in a pinch, or spend two GCDs (one to set up a shield and another to burst it) to consume a full shield for max healing.
Aww man, now I like this idea so much that I can't ever play Disc until it's implemented. I guess I'm sticking with Holy forever.