BRD/MCH having their own piercing?

[Kitfox]

Huh? How is giving them something that already exists going to break their dps? Like, it makes no difference if a DRG puts up piercing or it's the BRD/MCH.. Same effect.

It matters from balance perspective. You have to think in terms of how much dps a class is bringing into the party. DRG doing piercing means that each Ranged class in the party adds up to the amount of dps provided by the DRG. If Ranged classes could provide their own piercing debuff, that would mean that their personal dps would go up by 5% even without DRGs, so while DRGs' personal dps would be unaffected, their total provided dps would go down by 5-10%. DRG would become a dead class and nobody would want them.