The problem with this set is that the most prominent type that Sky Attack deals SE damage to (fighting) actively resists Snarl.
This set is only relevant against [Bug or Grass]/[Ghost or Psychic] types. This currently means only either against K-Exeggutor or Celebi. Decidueye joins these ranks in Gen 7, but other than those cases you're better off running double flying or double dark with it.
EDIT: Trevenant and Gourgeist will also join this camp in Gen 6, as will Dhelmise in Gen 7.
