What if casters had element resistance debuffs?

[HyoMinPark]

By that logic though the current debuffs for slash pierce and blunt should just be weapon resistance down instead of individual.

I wasn't arguing about those debuffs, and they don't have anything to do with what I said. Having 6 different elemental debuffs would be entirely way too cumbersome for casters to manage (compare to RDM who, if they wanted specific elemental resistances down, would have to apply each specific debuffs basically every other attack), and they would really only benefit a singular caster for any extended period of time ("fire resistance down" and BLM in Astral Fire). As it stands with the physical debuffs, yes only MNK benefits from blunt, but the entirety of a BRD/MCH/DRG rotation benefits from piercing, and the entirety of NIN/SAM/WAR/DRK/PLD benefit from slashing, not just a couple GCDs before having to switch to another debuff, which is what you would have to do if there were individual elemental debuffs.

If players want a "magical resistance down", it would be much better (and much easier to manage) to do a sweeping "magical resistance down" rather than have to switch debuffs based on your next GCD. Plus, SMN/SCH/AST would benefit from that as well, all of which have unaspected magical damage.