Some say that the metric of a good healer is how much raw, effective healing they can put out, and others say if everyone was alive at the end of the fight, healing is fine and doesn't need to improve.
I fall into the first group, but I try not to get caught up in healing meters because I know they are unbalanced, (and by unbalanced I mean some classes are consistently miles ahead of others) and I am growing more convinced that they are intended not to be 'balanced'. But wait, why would blizzard intentionally design healers to be unbalanced?
My suspicion is that aside from having 'niches', blizzard doesn't count 1 point of absorption as 1 point of healing (the way healing meters do now). In my opinion, 1 point of absorption is worth more than 1 point of healing, since you never take the damage to begin with and don't need time (which is one of the components of HPS) to heal back the damage.
So basically if a druid anticipates big raid damage coming and applies rejuvs ahead of time, and then a disc priest blankets the whole raid in spirit shells and power word shields before the damage goes out, it makes the druid look bad on the meters (and if their raid leader only cares about throughput, could risk their raid spot) even though he or she did exactly what he or she was supposed to do. So if i were designing the game, I would put disc priest and holy paladins' maximum theoretical throughput of combined healing and absorbs slightly lower than druids' (random example healer with no absorbs) since the druid relies on time after the damage is taken to heal back the damage, thus providing a chance to overheal, which as we all know doesn't count as effective healing.
on the order of disc priest's heal+divine aegis totals to 95 (60 heal +35 absorb or whatever ratio) and druid's single target heal heals for 100. these are made up pretend numbers, but the spirit of my design is that since raw healing isn't as potent as absorbs, absorbs should cost more time and energy to apply the same amount.
Fight mechanics currently, and always will favor absorbs over raw healing. It's just the nature of the game. So as long as 1 point of absorb=1 point of healing on recount/skada/world of logs, disc will always seem overpowered and people will whine.
So the solutions are: