Might be they're actually fine with healing legendaries being in this boat. What we do would be classed by some as utility. I don't really care. Healers are balanced well enough this expansion for my tastes. Shoulders brought me up a few percent. Nothing crazy. Healed everything fine without them before they dropped.
3.2% of my healing the last boss we did. About as good as any great piece of loot with something special about it.
I'd actually imagine Drape of Shame is much more impactful than any legendary we have access to atm. Just much harder to see the impact of on a parse.