Defensive Tornadus without Assault Vest is definitely an uncommon set, but many underestimate its power.
Tornadus-Therian @ Leftovers
Ability: Regenerator
EVs: 8 HP / 252 Def / 236 SpD / 12 Spe
Impish Nature
- Tailwind
- Knock Off
- U-turn
- Taunt/Toxic
Although the primary purpose of this set is to set up Tailwind and U-turn away to support teammates, it can effectively bluff offensive Tailwind and manage to get a Knock Off on the likes of Chansey and can also be a thorn in the side of stall, depending on whether you want to go with Taunt or Toxic. Taunt in general is a valuable asset on Tornadus-T that is often overlooked.