That set is in no way the best, Mullet, seriously. Dragonite cannot setup a Sub against anything other than on a switch.. to Metagross or Swampert which will both brake the Sub with ease next turn while you hit them for some damage, and yay, you just wasted 25% of Dragonite's hp, while you could have just T-bolted or Focus Punched on the switch instead. HP Grass (or HP Fly) over Sub makes that set alot better, but (imo) it's still inferior to the set shanecdavis posted. And no, Fire Blast isn't better than Thunder on that set competitively, as Thunder hits Milotic and Suicune on the switch, which wall Dragonite otherwise. Though competitively I find Focus Punch to be more useful on that set than Earthquake, as it takes out a nice chunk from Swampert on the switch, and makes those Ice Beam Blisseys, Regices and Snorlaxen think twice before switching in as well, though Metagross becomes somewhat of a problem then, but not a big one.
So basically yeah, use the set shanecdavis posted.
Oh and Lugialord, Dragonite doesn't learn Rock Slide.
np: Dream Theater - Hollow Years
Have a nice day.