What I've said before and I stand by is just treating the healers the same way as the tanks as far as their gameplay is concerned--having around the same balance between offensive and defensive hotbar actions--one with a little less like WAR and one with a little more like GNB.

The concern is a chunk of players are bored playing as healers because there isn't enough to heal and next to nothing to do during the gameplay deserts between instances of necessary and/or emergency healing. Every effort to increase the necessary amount of healing makes the role less and less accessible to the novice and intermediate players as any lapse in their ability to meet the healing requirements can result in party death. That's not to say healing requirements cannot increase at all, but there is a limit to how much is realistic, and that limit will not resolve the issue of healer boredom alone.

Everything shy of Extreme, Savage, and Ultimate is not subjected to enrage timers. I don't care what anyone says, what SE thinks, or what some forum white knight will scream is "elitist" if it means someone cannot parse 99% by turning on their turbo controller, there is no necessary DPS performance bar for healers to clear anything that matters to anyone who otherwise could not keep up with whatever mild DPS tools the healers could have if they were treated equally to the tanks. It creates gameplay that the player is allowed to approach at whatever pace they are comfortable with at no consequence of that player's ability to progress any storyline, whether the MSQ or a secondary storyline like the Pandemonium story, their ability to do their daily roulettes, or their ability to engage with alternative content like Eureka, Bozja, Deep Dungeons, or Variant Dungeons. And in fact, in regards to Extreme and beyond, it actually reduces how much damage you lose per GCD healing you rely on because less potency is baked into every individual cast of your filler spell.