Miasma Valley + Absol + Metagross= Nothing that isn't Grass or Psychic with 60 HP even touches the board.
Further more, SP Lv.X's, (notably Garchomp C Lv.X, who devestates the strategy), won't be able to Level up when you shoot it with Octillery. The only way to get around this is to bench 2 Garchomp C's in the same turn, but still, they are both a Spiritomb drop + Ninjask attack away from a 2 prize liabilty. It's a big set up with a big pay off.