I think the main problem with Priests and PDs is the convenience they have in their ranks, allowing someone to pick both without sacrifices, and their buffs applying at full potential to the whole party.
The classes alone are not so strong at all, only filling their roles normaly, but combined they can be the best support in the game and have almost no counterplay.
Example:
If you build something like Cleric -> Priest3 -> Monk3, with stone skin you can be strong against melee classes, but will suck against magic and CC ones.
If you build Cleric -> Krivis2 -> Bokor3 -> PD, with bloodletting you can counter nearly every CC in the game, but will be punished when a Doppel catch you with cyclone or a musketeer with snipe.
And… if you build Cleric2 -> Priest3 -> Chaplain -> PD, you will have the strongest skill against melee, the strongest skill againt CC, and the best healing of all classes, leaving you open only for magic nukes, but with enough CON and revive, this can be countered too.
So, I disagree with nerfing the skills on the caster so much, but agree with nerfing them to the party, like halving the effects for them. I hope IMC create new especific classes with rank 4 or more status ailments and gears focused in high block penetration to people who want to counter Priests and PDs.
(sorry if I made some mistakes in my english)