People are stupid. the only way Shandera can OHKO Roobushin (mine, at least) is with Specs Overheat.
Here's THE set that got me in the top 10.
Roobushin @ Leftovers
Guts
Adamant nature, 80 HP / 88 Atk / 100 Def / 240 SpD
Final stats are: HP 371, Attack 371, Defense 251, and Special Defense 226.
~Mach Punch
~Drain Punch
~Bulk Up
~Payback
Same old moveset, but way better EVs. Those EVs are what make this set such a beast to take down.
See that special defense? Not even Soul Dew Latios OHKOs with Draco Meteor. The idea is to bring this on a predicted will o wisp (or toxic, but beware the exponential damage). Bulk Up once and start killing stuff. Starmie, Espeon, Latios, Shandera, Ludicolo, non specs Sazandra...none will ohko, whilst you will either OHKO with Drain Punch. If they somehow survive, Mach Punch. You can set up on CB Scizor locked into Bullet Punch, Tyranitar, Nattorei, Burungeru, or most bulky waters, for that matter.
This Roobu almost always beats even special based pokes one on one, but can't take too much special assaults, which is why I highly reccomend wish support. Then again, isn't not totally necessary, considering you can heal with Drain Punch.
As far as counters go, Zapdos swallows this, resisting your STABs and doesn't mind Payback. Skarmory has brutal defense, whirlwind, and brave bird. Hippowdon and Gliscor can't touch you at all (hippo can Roar you, though) and after a bit too much turns they're guaranteed to go down, provided you bulk up even once.