I know I've posted this set in the Official, but perhaps I should have posted it here (plus, I've modified it):
Yveltal @ Life Orb
Ability: Dark Aura
EVs: 136 Spd / 252 SAtk / 76 Atk / 44 HP
Mild Nature
- Dark Pulse
- Sucker Punch
- Oblivion Wing
- Substitute
As stated before, the 44 HP is for 101 Substitutes, max Special Attack for the obvious reasons, and the 76 Attack is just enough to ensure a OHKO against Mega-Mewtwo Y with Sucker Punch after Stealth Rocks. The rest is dumped into Speed because why not? I'm still a bit unsure of this, as it may not need so much Speed investments and maybe a bit more into HP or Attack.
This set has a lot of potential, i was thinking on something similar, since Life Orb boosts his power even further and lessen switches, specially coupled with dark aura. Being dark and flying type gives it two good immunities to switch into them and set up substitute, which can Block ditto, unwanted status or pseudo status, faster priority moves and forces foe to attack and ease sucker punch prediction. Sucker Punch also provides necessary priority to either dent or K.O. some faster or weakened threats.
Due to it's high base speed it can outrun most of the Uber tier without much investment, this benefits greatly the use of oblivion wing, which in tandem with substitute will keep Yveltal healthy enough to keep using substitutes and it's life orb to gather more damage on your foe's Pokémon thanks to Yveltal great offenses and it's ability. Dark pulse gives it a much more powerful stab option with the chance to flinch which can be dangerous for your opponent if you are behind a substitute plus also giving it a reliable stab coverage move.
The only thing i have to differ from its the speed EV's and nature it needs i rather run Yveltal with a Hasty nature to ensure outrunning almost all of the Uber tier, plus since most of the uber tier it's special with it's natural high hp can take a few special hits and thanks to substitute doesn't actually have to fight directly with physical attackers. 48 Hp instead helps for 101 substitutes but also reaches a magic life orb number which helps to get one extra switch on steal rocks and Survive after 40 times of Life Orb Recoil Alone. Since Life Orb and Dark Aura will augment it's Sucker Punch Power with 28 atk EV's it's more than enough to dent or K.O. weakened/faster Pokémon.
208 Spa Reaches 350 Special Attack which it's enough to ensure high damage on your target's thanks to life orb and Dark Aura. Finally 224 Speed reaches 319 Speed which is enough to outrun most of the Uber tier and also take advantage of it's substitute and Oblivion Wing. At least that is how i see him, but also a SubRoost set will be excellent if you don't actually care about fighting things like Mega Mewtwo Y and Similar faster Pokémon. Up next Some Calcs;
- 208 SpA Life Orb Dark Aura Yveltal Dark Pulse vs. 252 HP / 0 SpD Ferrothorn: 196-231 (55.6 - 65.6%) -- guaranteed 2HKO
- 28 Atk Life Orb Dark Aura Yveltal Sucker Punch vs. 252 HP / 252+ Def Blissey: 351-413 (49.1 - 57.8%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery
- 208 SpA Life Orb Yveltal Oblivion Wing vs. 0 HP / 4 SpD Darkrai: 181-214 (64.4 - 76.1%) -- guaranteed 2HKO after Leftovers recovery
- 208 SpA Life Orb Yveltal Oblivion Wing vs. 252 HP / 0 SpD Forretress: 251-296 (70.9 - 83.6%) -- guaranteed 2HKO after Leftovers recovery
- 28 Atk Life Orb Dark Aura Yveltal Sucker Punch vs. 252 HP / 252+ Def Cresselia: 244-291 (54.9 - 65.5%) -- guaranteed 2HKO after Leftovers recovery
- 208 SpA Life Orb Yveltal Oblivion Wing vs. 252 HP / 4 SpD Assault Vest Conkeldurr: 315-374 (76 - 90.3%) -- guaranteed 2HKO
- 28 Atk Life Orb Dark Aura Yveltal Sucker Punch vs. 252 HP / 0 Def Goodra: 259-305 (67.4 - 79.4%) -- guaranteed 2HKO