Fire Fang will always do squat to Skarmory, even after a Swords Dance. Samson introduced me to this moveset, and it happens to be one of the best:
Garchomp @ Life Orb/Leftovers
Naive Nature (+Speed, -SpDef)
EVs: 252 Attack, 252 Speed, 6 Attack
- Earthquake
- Dragon Claw/Outrage
- Swords Dance
- Fire Blast
Most Special attacks Garchomp doesn't resist will put a hefty dent in him either way (and any decent Ice attack will OHKO him), so Naive gives him the max Speed to outrun things he needs to, like Jolly Electivire, and allows you to get the full potential of Fire Blast, which is basically a 2KO against Skarmory.
I wouldn't totally recommend Outrage, since Swords Dance gives it the same, if not more power, minus the confusion. Without Fire Blast, Skarmory walls him no matter what, even with Fire Fang. If Skarmory is down to about 50% HP, Fire Blast from this bad boy will likely KO. Oh, and Fire Blast also takes care of Tangrowth, who I've been finding extremely annoying lately, and would otherwise take damage from Garchomp without a problem.
And coming from a guy who uses Skarmory, this moveset scares me, because Garchomp threatens to sweep at any given time. After a single Swords Dance, Earthquake is an OHKO on Blissey, and everyone knows how truly difficult it is to completely OHKO Blissey like that without a Fighting attack.