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VIT is the best right side, bar none in-progression. I've already had one clear save because of my VIT VI melds, that's worth it's weight in-gold over some points in Crit/Det. Of course once you get content on-farm, and have more 330-340 left sides you can shave them for other stats. Remember it's not so much about you doing mechanics correct, it's that there are seven other people that could mess something up, putting your HP at even more risk.
One DH VI meld minimum somewhere, usually you'll find a s lot for this where Crit/Det might already be capped on the gear. You can go higher to help your chances even more. But absolutely it's a gain to have one meld otherwise you are at the mercy of a party-buff like Bard's Battle Voice to even trigger DH on your damage.
Crit is my favorite choice among all-healers, mainly because of damage and healing impact. You don't depend on a crit heal so much since healing is scripted, but it can be nice if your Medica II ticks do crit because that could save you a GCD of healing somewhere.
PIE is a personal choice, and if you are progressing savage or doing traps, it never hurts to have a bigger pool. Things go wrong and you'll be able to do more in-a-pinch.
DET is ok, it's usually slotted where I can't even improve Crit anymore on the gear. Still seems you need a lot to make a material impact, but this affects every skill you have so there is definitely benefit.
SpS is ok on WHM, it's like a det to DoT/HoTs but enough of it also affects your gcd. Since raid healing is scripted you might have adapted to when and how you should heal something. Changing this too much might have you change your regimen a bit.
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Det, SpS, Crit for WHM. Pie as needed, which is very little for WHM. Vit in accs until you get a couple pieces of 330.