Aurumoth's design is pretty cool, you guys did a great job on it. As for it's OU career, unfortunately, I doubt it would be so great. It's idea is high-risk, high reward, but safety is better overall. Salamence can destroy a team, but Multiscale gives Dragonite a better chance at sweeping; Dragonite is usually preferred. Mixed stats cause a pokemon to lose a large amount of their usefulness in a single offense. This is compounded by Aurumoth's fairly bad offensive typing, which means it will most likely want more coverage. As a dragon dance sweeper, it is mostly outclassed by the the already mentioned Dragonite and Salamence, due to it's inferior offensive stats. Quiver Dance has only one real form of competition, Volcarona, but the fire moth also has superior stats and a more potent STAB in Fire Blast. Finally, it's only really useful ability is Illusion, No Guard doesn't seem particularly useful, while Weak Armor is pretty situational. Illusion could be where Auromoth gains a free setup turn, but then, It still can be revenge killed a +1 speed, but might not matter at all. So that's risky, like you guys intended. In the end, however, I feel most People will go for consistency rather than playing it risky.
This is just my opinion, However...
