I am quite sure reworking the healers and putting them back into PvE without upsetting certain balances in the game is a daunting task for the dev team. Since healer offense was never accounted for when creating DPS checks in the game along with having very few skills to do damage, giving them even one additional skill quickly changes the overall rDPS over the course of an 8-12 minute high-end encounter.
That is why such changes can't come mid-expansion, because if they did that, they would have to balance out the DPS by taking it away elsewhere. The quickest place to go for that are the DPS jobs, who would then ask, "WTF Flare get nerfed yo?" They have added skills back in the past, and have even done it this expansion; but like I said, someone takes a hit somewhere. When SCH got Energy Drain back SMN got Tri-disaster nerfed soon after. While it was known at the time the SMN was OP, this wasn't really the reason why SE nerfed it. Shaving a little bit off the top didn't really change that job all that much. They will typically go to whichever job that is causing the most damage that is not BLM or SAM. From my observation anyway.
For casual content, meh. They can do whatever, and not much changes. Things might die a little quicker, so yay. But what we quickly have to take into mind is that when 6.0 hits, healer DPS output no matter how it comes will be pretty much be set in stone. They might make some tweaks, and add (back) a skill or two lol. A way around that is by adding in AoE skills since those skills are impractical to use on bosses. A positive result to that is that dungeons and other AoE situations become more fun to do, which will increase the amount of healers in those queues.
But yeah. I really don't think there is way the devs can continue to not allow healers to contribute more to the damage pool without the playerbase releasing the chimps to eat their faces.