I also think, to a certain extent at least, secondaries vary with each healing class.

Like SpS for instance. On SCH it isn't huge, the biggest part of their healing comes from abilities. On WHM? It can be handy, they use more spells. Peity on WHM is essentially useless because of their insane MP regen but you might see benefit from some of it on the other two healers because they aren't as MP efficient overall.

I don't think there will ever be an end-all set of stat weights for "healers" sadly. Even if someome can crunch the numbers for them individually I don't think they'll match up saying universally x is the best stat y is the worst, the ways they heal are too varied.