Today I attacked a Cocooned Phase Spider with my Wingmaster Cleric. Healing Winds did not trigger, even though the ability text describes it as triggering on successful attacks. In practice, I'm guessing it counts whether damage was dealt or not.
Unable to reproduce. Please note that Healing Wind will not heal the champion with the ability, only other champions.
My apologies, I have reread the text; the champion was likely not within 5 spaces of the target. I'm sorry. -- I did also encounter another thing that was definitely a bug: Wingmaster Cleric trying to heal a unit (according to the combat log) that had been previously destroyed, with no effect on anyone on the field. But I didn't mention this because I have no idea how it happened. I'll keep an eye out for it, though.