Your gear is definitely fine for coil.

Speaking from a WHM perspective, I would view determination as being the most desirable secondary stat, more healing is always good. Once content is farmable you may want to play with accuracy?
Piety is a largely wasted stat, I never run OOM and at the end of the day, leftover mana is wasted stat. Spell speed just means spending more mana for the same result and is, IMO, a dead stat (having quicker GCD's is good but you need SO much speed for that, it's pretty irrelevant). I remember reading way back when stat weights were originally still being fathomed out that healing per mana and healing per GCD is optimised with determination.

Have you thought about crit? I know from the scholar that I static with that crit is nice for big shields and could help mitigate the spikey damage incoming and allow for more DPS to be pushed out.