The sky isn't falling on Dark Knights

[Launched]

It's actually not the same, it does more in grit, and a DPS loss out of grit.

with -20%(grit) and +20%(DS) = +0%, that means its potency is 650 +0%, unaffected by the stances.
w/o grit, that means its 520 +0%(no grit) +20%(DS) which is 624 potency.

so you lost 26 potency being out of grit.

That's not how it works. +20% and -20% don't cancel out, they're multiplicative.

Out of Grit:
380*1.2 = 456 potency

In Grit:
475*1.2=570 * 0.8 = 456 potency