Honestly, Masquerain is completely outclassed by Volcarona and even the likes of Venomoth. Even its onlt possible niche, baton passing butterfly dances, it is outclassed in by Venomoth, who has Tinted Lens, Sleep Powder and can actualy take use of the boosts. Venomoth also has access to Toxic Spikes if your into that. I really don't see Masquerain rising up the ranks, even when UU comes into fruition.
Also why was this necro'd, let it rest people.
Its not outclassed by Volcarona because its presumably going to be in a different tier. And Venomoth and Masquerain have 2 different abilities setting them apart. And Masqerain arguable gets the more useful moves for sweeping. Water/Ice/Bug is better than Poison/Bug/Psychic really.