Ok, so i've fought Diantha numerous times with Yveltal, and after yet another League run I have decided to ask, what would happen if Diantha's Gardevoir traced Yveltal's Dark Aura? One Dark aura by itself increases the power of all Dark-type attacks by 33%, so would it stack if two Dark Auras were to be put into play?
Yes it appears so
While this may not be right, it seems Showdown has it as the Dark Aura boosts are able to stack.
Synchronise Specs Gardevoir using HP Dark against a Yveltal
Damage varied between 11-13% roughly
Dark Aura (Traced) Specs Gardevoir using HP Dark against a Yvelta (Same evs and everything)
Damage varied between 15-17% roughly