Well, one of my best offensive Yveltal sets is:
Yveltal
Life Orb
Trait: Dark Aura
EVs: 72 Atk / 252 SAtk / 184 Spd
Hasty Nature (+Spd, -Def)
- Dark Pulse
- Sucker Punch
- Oblivion Wing
- Taunt
With Hasty nature, this Yveltal is fast enough to Taunt even standard Gliscor in Ubers, making him a great stallbreaker that can do a massive damage on Giratina, Ferrothorn, Groudon or anything that switch in with its main STAB Dark Pulse. He even drills holes on opponent team with the combo Dark-Punch.
This set focuses on predict-and-switch into walls. Yveltal stops almost all of them with Taunt then he'll attack the switch-in. Just calculate a Dark Pulse and a Sucker Punch on anything that doesn't resist it. Even though his Attack is pretty modest at 316, Sucker Punch does ~ 55% HP on a usual Palkia.
Oblivion Wing, of course, is the best healing STAB for this offensive set since this Yveltal doesn't have Roost. But if you use Roost, you'll lose the ability to, maybe, take a 45% HP of 260 Spe (too common) Xerneas.
Just use the scout-Scizor or Aegislash with this guy, they'll co-work effectively