The thing is that you can heal to what looks best on the meters. If all healers in your raid are going for max meters you'd wipe a lot. I think healing is the hardest roll to evaluate tbh. A tank you can see his threat in the raid, the cooldowns he uses, timing of taunts. DPS yu see during the raid what damage they do and what damage they take that they shouldn't, you easily visually see when someone is not switching targets or holding DPS during a certain phase.
You should also put in a bit on how to heal during trash/faster clears. As more and more content will be available guilds will benefit alot from efficient trash clears.