Noivern should never stay in against an Aromatisse, especially one at completely full health. His best bet is to sub in Flamethrower/Psychic/Dark Pulse in that 4th slot depending on the situation and team comp. Boomburst - Dragon Pulse/ Draco Meteor - Air Slash/ Hurricane; are all moves he should have as they cover everything rather well. Focus Blast is also something he can utilize in that 4th slot, although I've never needed him to take out anything using it, except for maybe the stray Umbreon popping up.