Come to think of it... I would love if the abundance of healing actions we have nowadays could be pushed to their full potential with a redesign of how damage happens in the fights. This means that fights would need to be less formulaic, and that is a big design decision that would certainly need to impact retroactively old content - that's a lot of work, but it would be worth.
I don't play WoW nowadays, but I remember that healers actually compete against themselves in the healing meters to see how well the party survived with the least amount of overhealing. Here in XIV all I hear is dps placement among healers... I don't ever think I saw the discussion about "healing meters" here, because it's treated like a subproduct of the dps performance.
Though I remember healers there being homogenized in how well they perform at certain aspects of a fight, I do know that they spend most of their time worried about healing numbers (sans Disc priest for obvious reasons).