I'm suspecting that DH will end up being the best overall DPS stat for healers in the long term and as mentioned elsewhere, it's a good idea to throw at least one DH materia in regardless just to unlock the ability.

My personal preference has always been towards max piety first and foremost (after ensuring I have comfortably enough VIT for the encounter ofc) followed by whatever the flavour is for that tier. Currently I'm leaning towards crit even with it's nerfs due to the numerous different ways it benefits me right now.

As far as my leanings towards Pie stacking go, my reasoning is as such: In a perfect run it's just not needed I completely agree, you'll see actual gains elsewhere in this situation. However, I've been in statics with some of the best EU players out there over the years and if there's one thing I've learnt, it's that runs during progression with top level players are rarely ever smooth Boundries are always being pushed and tested, people will be greedy and if they think they can get away with it, they most certainly will. Having that extra MP regen gives me a much better buffer with which to handle the group ignoring/failing mechanics whilst also significantly increasing the odds of keeping my own personal DPS going.

Stacking DH is going to do nothing for me if I have to stop throwing rocks because my BLM didn't want to move.