Having done both AST and WHM to 90 now there is absolutely nothing a WHM can bring now that an AST can't do better. Currently. Things could change - perhaps there will be a fight where everyone explodes if you don't cast Liturgy?

The only reason to play one now is muscle memory or you like the look of Holy over Gravity.

Liturgy needs a rework- mana needs looking at and Misery needs to be buffed through the roof.

I hope I'm missing something here - the sky may not be falling but it does kind of feel like it.