Why would you put Skill Swap on it? You're giving the opponent immunity to all mental status.
You shouldn't Skill Swap this awesome ability onto your opponent, that would be silly; you are going to swap it to your ally. Do not forget that you are able to target your own guys.
And why would you suggest leftovers over Draining kiss? It's a weaker move sure, but you gain 75% of the damage inflicted, which is more than the 1/16 HP recovery that leftovers recovers, even after multiple turns, and the Sitrus berry only recovers 1/4 of your HP one time.
Leftovers and Sitrus Berries are passive, Draining Kiss requires you to move. Fake Out is a very common move in Doubles, so you are very likely to be Faked Out and to be double targeted. Aromatisse's strength is that it does not need to carry Mental Herbs in order to prevent Taunt so that you are able to survive deadlier shots with the aid of another item. Also, even when Draining Kiss is healing 75% of the damage it still is dealing pitiful damage, thus the healing is neglegtible.
Also, this set is made with at least Leftovers in mind. When you don't use a HP recovery item, Kangaskhan has a chance of 2HKOing your Aromatisse. Doubles are very fast paced, so Sitrus Berries actually are very powerful. It is equal to four turns of Leftover recovery, don't underestimate it.
And why invest 252 Evs into Hp rather than both defenses fully maxed? I get more HP = more HP, but if the defenses are maxed, wouldn't you be receiving less damage anyway so it negates the need for higher HP? And more importantly, why strategies for specific singular pokemon, wouldn't it be much more beneficial to have a strategy against specific types (specifically steel, poison and fire types two of which Aromatisse is weak to and the third can only do half damage to since there's only one singular attack, rather than leaving myself grossly unprepared by building up a pokmeon for singular opponents just to discover that those opponents aren't actually being used?) I think your movesets may need more explanation, which I would really appreciate. They're not that obvious on their own sometimes. Thank you very much for your reply though
In metagaming you gear your Pokemon for the most common and poweful Pokemon you can expect. Kangaskhan is one of the most common and powerful neutral hits you will take in the entire game, it is natural to take her as a threshold. Incidentally, you also survive CB Scizor's Bullet Punch, so we definitely have done something right. Don't even try to match Mega-Mawile, it definitely overkills you. We hope that makes sense for you: If you survive the stongest Pokemon, you will survive the weaker ones as well. As for the weaknesses, you have teammates; use them. Aromatisse is a support Pokemon first, especially in regards of Trick Room.
When making a good EV spread you need to be very conservative with points. Try to utilise the least amount of points in order to accomplish a certain goal. Aromatisse definitely wants to survive Mega-Kangaskhan and a few rounds of Rotom-W so that is the most efficient spread we have found. You can also try not to be 2HKOed by Charizard-Y's Heat Wave in sun but doing that hurts your physical bulk a lot and it is still easier to deal with than Kangaskhan (Rock Slide).
To be frank, we don't know how to assess your understanding of the metagame, therefore we have been a bit vary with too much exposition (expecting you to be an expert). This is the shortest way we can explain Aromatisse without writing a full-blown analysis.
