Originally Posted by
OmnysValefor
Yes, it does stack, but when you're comparing -15% defense down vs -30%, the choice is obvious (when you're considering one job or the other) and since Dia II is -10%, it's really a choice of -5% additional from an RDM or -30% from an NQ GEO since the geo, whms, or blms can provide Dia II.
Edit: And I get it, you'll come back and say RDM can simultaneously Frazzle, Distract, Dia, Bio, Paralyze and the list goes on but the combined potency of all those buffs is frequently not enough to outweigh what one or two (especially two) geos can do especially if melee aren't part of your strategy.