If you didn't pet swap and kept Selene out at all times, you could maximize the DPS potential as you wouldn't need to mess around with switching faeries. Fey Wind itself is pretty consistent and you can rely on it to give a buff on a fixed cooldown, especially if we were to compare it to AST's Arrow which is at the mercy of RNG. Could FW do with a slight buff? Hmm I'd say no mostly like as Metsonm stated, Selene just needs help with the entire kit and not just one action.