Hmm. I must say this is interesting, But I think a Choice Band would do better here, for an interesting twist.
Gallade (M) @ Choice Band
Role: Choiced Powerhouse
EVs: 64 HP / 160 Atk / 252 Def / 32 Spd
Impish Nature (+Def, -SAtk)
- Drain Punch
- Psycho Cut
- Shadow Sneak
80 Speed is worth being Scarfed on, but then You're basically Scarfing yourself to be a basic sweeper. But banding him, That takes his 125 Attack stat, and Shoots it up high.
With Ev's invested, to get his Defense to where he doesn't HAVE to go first, Hp gets a few to be slightly more bulky, Attack is obvious. And 32 Spd To outspeed things that Carry 80 Speed and have nothing to boost it.