False, Xerneas is the #1 most common fairy-type I encounter on Battle Spot. So it is probably the best representative for the type in my opinion.
I see more Xerneas in battle than I do Azumarill, Togekiss, Klefki, Mawile, the Blissey/Clefairy lines, Sylveon, etc.. well maybe equally as Gardevour as that one is very common too. but the rest, i can honestly say i dont encounter as much as i do an opposing Xerneas.
I rarely if ever see Granbull, Slurpuff, Aromataise, carbink, or any plant fairy
I think you already checked all the boxes..
Cant get any cheaper or more pathetic than the no-skill cheat move Dark Void.. anything beyond that is just overkill. You could add a "Dark/ghost" move to Smergal for the 1 in 10,000 chance you encounter a user with Magic Bounce (i.e. Xatu), which would make Dark Void backfire and instead put your Smergal (and team) to sleep causing you to ragequit like the trainers with Darkrai that I encounter on a daily basis xD.