ScraftyIsTheBest, why not run endure instead of sub on that set? You'll have an easier time getting down to 1 hp this way rather than relying on your opponent to give you a free turn to sub up. Also 4 hp EVs makes you die to 2 rock switch ins and prevents your 4th sub, btw.
But anyway, here's a set I just came up with:
Swarm Sweeper/Tailwind Utility Scyther
Scyther @ Salac Berry
Trait: Swarm
EVs: 252 Atk / 252 Spd / 4 Def
Jolly Nature
- Swords Dance
- Endure
- X-Scissor
- Tailwind
This set has two purposes: to sweep with +2 swarm boosted X-scissors at +1 speed, or to reliably set up tailwind for your other pokemon to sweep. The idea is to set up an SD on something that doesn't threaten you, endure as your opponent tries to kill you off with their check, then start firing off what are essentially +4 X-scissors. In the case that you can't set up an SD, you can set up tailwind reliably by enduring to get your salac berry, and then tailwinding as your opponent kills you off. The great thing about this pseudo-prankster tailwind is that you actually get all 3 turns to use it if they kill you off, and if not, you can hit them with a swarm boosted attack before you die. Once you sacrifice Scyther to get tailwind up, you can go into a wallbreaker or powerhouse of your choice, such as banded Druddigon. This set is intended for late game use, as if used without hazards or some prior damage on your opponent's team, chances are they have something that can live a hit. Pretty much only bulky resists or 4x resists can take a hit from this; a resist like Rotom-N is not a counter. This set needs to watch out for priority, as it'll often be sweeping at 1 hp. If only trying to set up tailwind though, priority should not be an issue as long as rocks are off your side, as Scyther is bulky enough to live most priority moves in the tier.
Some calcs against resists and bulky mons:
+2 252 Atk Swarm Scyther X-Scissor vs. 0 HP / 0 Def Entei: 53.63 - 63.34% (dies if rocks are up, and you endure its flare blitz)
+2 252 Atk Swarm Scyther X-Scissor vs. 0 HP / 0 Def Typhlosion: 71.71 - 84.84%
+2 252 Atk Swarm Scyther X-Scissor vs. 248 HP / 0 Def Escavalier: 48.68 - 57.43% (ok you can't beat this without prior damage lol)
+2 252 Atk Swarm Scyther X-Scissor vs. 4 HP / 0 Def Rotom: 89.25 - 105.37%
+2 252 Atk Swarm Scyther X-Scissor vs. 252 HP / 252+ Def Tangrowth: 105.94 - 125.24%
+2 252 Atk Swarm Scyther X-Scissor vs. 240 HP / 16 Def Amoonguss: 106.52 - 125.4%
+2 252 Atk Swarm Scyther X-Scissor vs. 4 HP / 0 Def Omastar: 102.12 - 120.21%
At +1 speed, Scyther outspeeds the entire metagame except for scarfed Galvantula and Cinccino (not very common) and Manectric (speed ties). Moltres and Emboar are the two most common things that wall this to hell, but there's also Aggron, Poliwrath, Qwilfish, and Magneton. Sure, mono-bug isn't very good coverage, but +2 and swarm boosted, most resists still take over 50% from an X-scissor, requiring little weakening to get past. And even if you can't get past Scyther's counters, you can get an almost guaranteed tailwind up with endure + salac, paving the way for the rest of your team to clean up.