Right now, WHM is closest to what traditionally was RDM in this series. PoM is pretty much Dualcast/Chainspell and they have the strongest offensive spell selection of the healers. I'd personally like for them to continue this trend. Definitely some Cleric Stance traits for synergy between weaving healing and offensive spells. Assize is excellent for this. If WHM is about raw power, that should count both offensively and defensively; make their single target, higher DPS more sustainable, maybe something a bit like Freecure, but for Aero or Stone.

But even with an offensive buff that still won't make them as appealing as an AST or SCH in raids, but it's a start.

(That being said, WHM right now is a beast in dungeons and buffing their AOE would probably be a terrible idea. I already out-DPS most DPS on trash).