I'd typically just avoid crit WHM builds.
The aggro generated for overhealing is obscene and a massive concern for any WHM.
Consider your pain points playing WHM or SCH, then spec around those to either minimise the issues, or, be a boss and maximise healing potency.

Piety is my favourite statistic mainly because that SoS cooldown is horrid if you mistime it or require it for enmity removal.
Healing potency isn't a concern I've ever noticed. Det? No thanks.
SS is nothing important. All boss mechanic dps is either insta chunk, or 3-5 second CD. You pre-cast, or you spam cast which matches their speed.
Until a boss fires out AoE spells <2.5s, I won't be specing SS.

Crit SCH.
Pie WHM.

(IN MY OPINION)