How would you feel if shields had no upfront healing?

[BungleBear]

What you are describing here is true and highlights a very interesting quirk that is unique to healing: the less you know about your job and the less you know about the encounter, the more fun healing is because the damage that you and your team takes is seemingly "unpredictable" (not actually unpredictable, but with low skill and/or experience, it can seem that way). This means your need for healing is something you aren't planning for and must adapt to on the fly, which is a thrilling and adrenaline-pumping experience. That said, this aspect is transient. The better you get at healing and the more you learn new fights, the more that thrill evaporates.

I'm not convinced that this phenomenon is unique to healers. Consider melee DPS, for example. When you start doing a new encounter, you're thinking about how to maintain maximum uptime. At first, you play it safe, but as you learn the fight, you start to test the limits. Think about the first time you try to greed a GCD, and it works! That would be pretty thrilling. But after you've figured out the timing so you know you can reliably greed the GCD, it's not very exciting any more. A new encounter is like a puzzle to solve. Everyone has their own little puzzles to solve within the larger puzzle. Solving the puzzle is more engaging than merely repeating the solution. But that applies to everyone, not only to healers.

Healing is dull and lifeless when you're doing the MSQ, when you're grinding FATEs, when you're doing Roulettes, when you're doing Beast Tribe Quests, when you're farming Extreme/Savage fights after having learned them, when you're farming unsynched content, when you're doing treasure map dungeons, when you're doing your 24-man alliance raids after the first few weeks when less people are failing mechanics, when you're hunting marks, when you're farming deep dungeons, when you've ultimately learned how to optimize your healing and thus have significantly more time to mash the Glareficoil button like you're playing a Mario Party minigame.

I don't think the activities you've listed are especially engaging for any role, not only for healers. But I think that's fine. Not all content needs to be super engaging. They call it "grinding" for a reason: it's just a mindless repetitive activity. I don't do treasure maps for engaging gameplay. I do them to have a laugh with friends. When I want content that requires a high level of focus and attention, I do savage or ultimate. But when I just want to relax and turn my brain off, I do an alliance raid or a jumping puzzle in the Gold Saucer, or whatever. I think it's good that the game provides this kind of variety.

It seems to me like you're looking for engaging gameplay in the wrong places. If you want to be challenged, don't grind fates, or do treasure maps, or farm fights that you've already cleared.