One of the challenges with healing in MMOs is that your role contribution scales inversely with content familiarity; as your team's gear and mechanical comfort increase there is less damage taken and thus less healing for you to do.

This issue doesn't just occur for mastered content; if an encounter is undertuned your healers will have to cope with the missing damage. This is typical of raids in many MMOs, where "trash" pulls put healers to sleep in between boss fights.

From what I've read of FFXIV, most of the game's content just isn't tuned to give healers enough to do, resulting in an expectation that healing jobs will push out damage between healing GCDs. This could be considered undertuning or a deliberate design decision. Either way, healers are expected to output damage as well as heal, to the point where 4.0 healer DPS reductions are a significant concern within the community.

I personally enjoy devoting myself to healing mechanics on healing roles. Is 4.0 shaping up to require more healing, or will it be healing light like 3.X?