I still maintain that Sub + 3 Attacks will be Hoopa's best set, if not one of the only usable ones in OU. Substitute gives it a psuedo-protection against Pursuit users and it has Focus Blast to make quick work of Dark types.
Hoopa @ Leftovers/Life Orb/Sitrus Berry/No item
Ability: Magician
EVs: 4 HP / 252 SAtk / 252 Spe
IVs: 0 Atk
Timid/Modest Nature
- Substitute
- Psyshock
- Focus Blast
- Shadow Ball
It also completely walls Chansey behind the Sub and will be a pain to Stall in general, while still being very useful against offensive teams as well. The Knock Off, Pursuit and Sucker Punch weaknesses suck, but the Sub kind mostly makes it better. I see Hoopa being viable in OU and probably ending up in RU, where it will likely be a force, but still has Spiritomb as a hard counter plus Doublade, Shiftry and others to revenge kill it. It will be horrible in UU though, where the two most common Pokemon in the tier, Mega Blastoise and Hydreigon, both give it a really hard time.