What stats should I put in my gear

[LegoTechnic]

From the patch 4.01 notes in Resolved Issues:

"An issue wherein the scholar action Fey Union would always restore critical HP under certain conditions."

Does this have to do with the DH stat making Fey Union much stronger?

Yes. If they fixed it then expect Fey Union to heal for 30% less per tick if you have direct hit melded somewhere.

Sadface.

In terms of what materia you want, Crit or Det will probably be a safe bet for most healers, but consider VIT for your right side accessories if you intend to hit Omega savage hard. Melding VIT was exceptionally useful for all classes, especially while learning.

You may also consider some Piety pieces on gear that is otherwise capped in your desired stat. Spell speed is an option, but with the job changes it really lost a lot of appeal, and you need quite a lot of it to notice.