Well it's stil a gain of heal and DPS even little

Since you can only add piety or SS
And diurnal sect is already à speed cast bonus
And no need for piety when we have a huuuuge mana regen
Acc is useless if diurnal main heal

It leave only deter as secondary stat which also give healing and DPS bonus
(ss Does too but i think that deter is still better in the end)