Stat Priority as a WHM.

[Tranquil]

Enough PIE > Max DET > all the others. Just my opinion, though.

CRT is not too bad, but a WHM doesn't really synergize with it that well. This game's fights are really scripted so in my opinion SPSP is not really a good stat, because you will not be spamming enough heals to notice any noteworthy differences, except in very exceptional situations (or if your co-healer is terribad).

It's all in the pre-casting and pre-mapping of an encounter and trying to minmax your resource usage. This is why you should always aim to have enough PIE, then go for DET for stable gains.

A "wild card" 2ndary for a WHM is accuracy, but this mainly applies for crafted gear only and the "bonus" points on your Nexus once PIE+DET are capped. Can make a small difference with that Aero accuracy and Fluid Aura DPS over time in veeeery tight DPS check fights. (FCOB).

[Taika]

Enough PIE > Max DET > all the others.

This is true. And note that you shouldn't aim for max PIE, but enough of it to be comfortable in the content you're doing.