If you are a WHM without Swiftcast, you are holding back your team at endgame

[Doo]

no, healers are not supposed to ensure their groups win by covering for the failures of their group no matter how much you want this to be true

Yeah that's more of a definition of team play rather than healer role. Players are suppose to help each other out and do everything they can to help the team win. Like if a dd or healer accidentally aggros a boss, it's not the tanks role to get the add of them cuz the other players messed up but it would be a nice team play gesture.