Presence of Mind - better, but still useless, suggestion how to fix it.

[Menae]

It literally shaves milliseconds off the casting time for cure. You get maybe 1 extra cure out of the whole duration, 2 maybe with the 'enhancement'. The simple fact is that at higher ranks, there's a significant diminishing return on spell speed, so much so that the effect of POM is so tiny that it makes very little difference overall.

Powerful? We have very different definitions of the term.

As for why I don't tend to use it? Simply put, it has a casting 'time' of its own. Sure it's classed as 'instant' but as anyone who's used Benediction knows, instant is anything but. If I need beefier cures, there's Divine Seal which has the same 'cast time' but guarantees my cures actually work harder for me. A far better payoff than PoM and on a shorter cooldown to boot.

For Holy, maybe it has some small utility. But it's a damned expensive spell, and it's easy to deplete your entire MP bar if you decide to spam it. A holy spamming white mage isn't doing her job of healing the party either, so it's very select in its usefulness.

Yes, it shaves milliseconds off the cast time of Cure. Three hundred forty milliseconds. I'm not trying to stack spell speed on my end - I prefer det, personally.
Still, my Cure 1 time without PoM is: 1.92 With it: 1.58 Stone 2 w/o: 2.4. With: 1.97. Holy: 2.88 to 2.37. Also note that since the recast time is 2.4 seconds

PoM allows me to put seven Stone 2/Aero 2s into a 15 second period instead of six. It lets me fit in nine Cures instead of seven in a 15 second period. That's damage or healing that otherwise would not be there (though it does come with attendant mp costs). Whether you NEED the healing or not is certainly a good reason to not use the skill, but saying it's not as good as Divine Seal therefore you want something else on your cast bar is overreacting. I'd also point out that PoM does increase your cast speed on stoneskins, esunas (lol), slowcast raises (lol), protects, whatever. Probably not the most important thing in the world, but hey, why not, right?