Tailwind + Healing Wish sounds alright but got to go with...
Physically Defensive
Shaymin @ Leftovers
Ability: Natural Cure
EVs: 248 HP / 252 Def / 8 SpD
Bold Nature
- Aromatherapy
- Giga Drain / Seed Flare
- Leech Seed / Hidden Power Fire
- Protect / Rest
Decent team support set; Aromatherapy, good physical bulk and Natural Cure (with some critical type neutralities compared to Celebi) give it a small niche in OU. A physically defensive spread makes the most out of its ability to handle M-Gyara, Lando-T, Azumarill, Keldeo and so on:
252 SpA Choice Specs Keldeo Secret Sword vs. 248 HP / 252+ Def Shaymin: 150-177 (37.2 - 43.9%) -- 99.8% chance to 3HKO after Leftovers recovery
252+ Atk Mold Breaker Mega Gyarados Crunch vs. 248 HP / 252+ Def Shaymin: 118-139 (29.2 - 34.4%) -- 99.7% chance to 4HKO after Leftovers recovery
252+ Atk Life Orb Bisharp Knock Off (97.5 BP) vs. 248 HP / 252+ Def Shaymin: 160-188 (39.7 - 46.6%) -- guaranteed 3HKO after Leftovers recovery
252 Atk Landorus-T U-turn vs. 248 HP / 252+ Def Shaymin: 120-142 (29.7 - 35.2%) -- guaranteed 4HKO after Leftovers recovery
252+ Atk Choice Band Huge Power Azumarill Play Rough vs. 248 HP / 252+ Def Shaymin: 193-228 (47.8 - 56.5%) -- 30.5% chance to 2HKO after Leftovers recovery
Aromatherapy is the crux of the set, but there are two main paths for the remaining moveslots - Giga Drain / Leech Seed / Protect, or Seed Flare / HP Fire / Rest. The former can be difficult for some offensive teams to handle, allowing Shaymin to 1v1 the likes of M-Metagross and standard M-Lopunny, while the latter is less of a liability against bulkier teams.