While I haven't seen a lot of healers that refuse to heal, I have seen a lot of healers that refuse to hardcast a single res. I've seen parties wipe in extremes/savage because the healer that's alive absolutely refuses to cast a res at all unless Swiftcast is up, so their cohealer stays dead until the next major mechanic while the healer that's alive just flings rocks, then the debuffs aren't given out properly and we wipe.