So I was battling Starpower at Ubers just now, and my Palkia used Aura Sphere on her Darkrai. I was aggravated to see that Darkrai lived with 2% HP (which cost me the match, I might add), and even more so when I ran the damage calculations post-battle.
252SpAtk Life Orb Palkia (Neutral) Aura Sphere vs 0HP/4SpDef Darkrai (Neutral): 109% - 130% (308 - 366 HP). Guaranteed OHKO.
According to the calcs, it would be physically impossible for Darkrai to live, the only other conditions were Rain, which wouldn't make a difference. Light Screen was not up, so don't suggest that, and I am absolutely sure that is what happened. So the question is, how?