Dragonite: B+ to A-
The original generation 1 Dragon is definitely the best dragon dancer outside of the Ubers tier. Dragonite takes the role of setup sweeper with dragon dance, similar to Zygarde, Mega Charizard X, Salamence, Even [sometimes] the Altarias and takes it to a whole new level. I'm going to be comparing Dragonite to Zygarde throughout this post, due to the fact that if you wanted a Ddance sweeper that's viable in OU, it really comes down to these two if you want to save that oh-so-precious mega slot. [Or Salemence if you're crazy]
As someone mentioned before, Zygarde gets Dragon Dance and Extemespeed. Dragonite also gets Dragon dance and extremespeed. However, Dragonite has the insane base 134 atk, but Zygarde has only base 100. However, Dragonite gets the all-powerful Multiscale ability, which pretty much makes Zygarde useless. What Multiscale does is when you're at full HP, you take 1/2 of the damage. Which means you can switch in on a super-effective move [So long as it doesn't crit] and then strike back. Here's a set:
Dragonite WeaKness Policy
Adamant nature
Dragon dance
Extremespeed
Outrage
Earthquake/Iron head
EVs: 252 Atk/252 Spe/4HP
You use Eathquake or Iron head depending on if you're concerned about fairies, since Dragonite doesn't really switch out once it starts boosting and Multiscale breaks. Due to Multiscale, your opponent should try to fire off a super-effective hit to OHKO, [or use a really bad hit to take down Multiscale, but then you start boosting anyways] which if it's the former, weakness policy will activate. Since Multiscale was there, you're probably around 50%, so use Dragon dance. Now, you're at +3 Attack, +2 Special attack, and +1 Speed. Time to start sweeping! Also, Talonflame doesn't outspeed Espeed. So if your opponent tries that, surprise them with Extremespeed! Dragonite is an amazing setup sweeper, capable of outspeeding everything with Extremespeed, and gifted with a perfect ability. Dragonite deserves more than B+, so let's move it up to A-.
Also supporting:
Clefable for S