As someone who is a Green-DPS through-and-through, I feel like they treat healing like its a required utility and not actual gameplay.
With DPSing, you have things like positionals, combos (or forms for MNK), weaving-oGCDs, maintaining/gaining gauges/stacks/resources, high-burst phases, and, in the case of NIN and DNC, a mini-game.
Healing is just: Use Shield before big damage, Use Burst/Regen after damage (most of which is done via oGCD while weaving your DPS spells), and some resource management (for WHM and SCH). (Having said that, healing harder content does require more skill-coordination and planning but still boils down to these fundamentals.)

I'm not saying they need to make healing more challenging and/or in-coming damage needs to go up but if the dev team is going to continue emphasizing Healer's healing kits without adding much else, they need to make the kits at least fun/interesting to play.