I personally use a smeargle that has substitute, spore, lock on, and sheer cold. See how that works? I personally like it for the wifi battle tower rooms.
That set has just got 'fail' written all over it. Intelligent opponents will switch out as soon as you use Lock On and anything with Substitute or Protect can just plain negate the OHKO since it requires a turn of charge-up, and let's not even get me strated about the sturdies. Anything that requires you to spend one turn solely on charging is doomed to failure. :\
Functioning Smeargle sets are;
Smeargle @ Salac Berry
Trait: Own Tempo
Jolly Nature (+Spd, -SAtk)
Extremespeed
Endeavor
Spore
Endure
Endures an attack to trigger the Salac, after which you put the current opponent to sleep with Spore and Endeavor away. Technically it has a one-KO minimum against anything that isn't a STAlker since sleeping opponents will have to be switched out, meaning a free hit with Endeavor which will be followed by Extremespeed.
Smeargle @ Leftovers
Trait: Own Tempo
Jolly Nature (+Spd, -SAtk)
Spore
Ingrain
Baton Pass
Substitute
Only for Baton Pass teams, Ingrain prevents phazing (Roar and Whirlwind) and provides constant HP recovery for the pokémon. True BP teams turn the switching restriction into a non-issue since all pokémon on the team have Baton Pass (Meaning, in effect, free switches anyway).
And finally;
Smeargle @ Salac Berry/Leftovers
Trait: Own Tempo
Jolly Nature (+Spd, -Satk)
Belly Drum
Spore
Baton Pass
Substitute/Extremespeed
There's also the Imprison/trap/transform edition, but that one doesn't really work in practice.