It will entirely depend upon how much damage needs to be healed, and if there is a return of the "only-healing healer", in which case WHM (and as it looks PLD) might be mandatory, and not outdated. I hope so. I would prefer a world where you NEED a Whm if you are not overgeared like hell to complete content, and can pick one of the others as support, simply because WHM is the most-played healer and thus should be the most-represented.