Healers have it easier than the other roles on this because all healers value Crit and all healers value Det. If you're doing progression, some VIT can also be useful, but again all healers benefit equally. If you go with those you're in good shape.

If you find you have MP issues on one job and want to add PIE but not on the other jobs, go pick up a piece of Anamos armor and slot a ton of PIE in it. The other two jobs can't wear it, so they won't be impacted.