Make the EV spread on the Dragon Dance set 252 HP / 4 Atk / 252 Spe. The 40 Atk EVs on your current spread don't really accomplish much, and with max Speed, you'll be able to outpace base 130's.
The 40 Attack EVs on that spread achieve more than Maxing speed. Dragonite falls short of the base 130s with Max Speed at +1 and still less than scarf 110s at +2. You are wasting those 40 EVs if you move them to Speed. Put them into attack like before because you are boosting it every turn.
[SET]
name: MixNite
move 1: Draco Meteor
move 2: Extreme Speed / Roost
move 3: Fire Blast
move 4: Superpower / Brick Break
item: Life Orb
nature: Quiet
EVs: 248 Atk / 252 SpA / 8 Spe
This needs a better EV spread because it is inefficient. Go with what I bolded and mention this spread in AC because it outspeeds Breloom and Gliscor.
80 Atk, 252 SpA, 176 Spe, Rash
Also, remove the ability tag and slash Brick Break... Multi-Scale is that good.
Also, I tested the rain abuser and it can be improved drastically. I've used this set on my rain teams for a LONG time now and I can confidently say it is an improvement.
[SET]
name: Rain Mix
move 1: Hurricane
move 2: Aqua Tail / Waterfall
move 3: Extremespeed
move 4: Roost
ability: Multi-Scale
item: Life Orb
nature: Quiet
EVs: 248 Atk / 252 SpA / 8 Spe
The water "STAB" is nice here. Aqua Tail is best because it hits Tyranitar the hardest out of the 3 and will hit neutral targets very hard from the physical side of the spectrum. Aqua Tail is preferred for power, as it does 50-58% to Bold Blissey in the Rain (Waterfall does 44-51%). Also, Hurricane + Extremespeed will beat a LOT of shit out there.
Also, I used a Dragon Dance Mixed sweeper on a Rain Team. I encourage some people to test it. It was stupidly effective. This is similar to Salamence, but Dragonite gets a safer Dragon Dance with Multi-Scale.
[SET]
name: Dragon Dance Mixed
move 1: Dragon Dance
move 2: Outrage
move 3: Earthquake
move 4: Hurricane / Draco Meteor
ability: Multi-Scale
item: Life Orb
nature: Rash
EVs: 96 Atk / 252 SpA / 160 Spe
The EVs allow for 236 Spe, enough to outspeed the genies at +1. You can shift the extra 56 EVs to speed to outspeed ScarfChomp at +2, HOWEVER you can lose important OHKOs on Tyranitar and Metagross with Earthquake which are crucial if you are using this on a rain team to abuse Hurricane (which you should because it has no drawbacks).
Also, I used this set extensively as well.
[SET]
name: Agiliscale
move 1: Agility
move 2: Hurricane / Dragon Pulse
move 3: Surf / Fire Blast
move 4: Roost
ability: Multi Scale
item: Life Orb / Leftovers
nature: Modest
EVs: 40 HP / 252 SpA / 216 Spe
This thing is a killer staller with Toxic Spikes, or a killer sweeper with regular spikes. Agility on the switch so that you are faster than everything. From here you can either attempt to stall for poison damage with Roost + Multi-Scale until they are in your killing range. Fast Roost with Multi-Scale is really realy good. The given EV spread is best with Life Orb, as its more about damage and less about stalling. However, Leftovers gives even more Multi-Scale abuse, which you should probably go with
248 HP / 252 SpA / 8 Spe, Modest, which outspeeds even base 130s after an Agility and gives you enormous bulk with Multi-Scale.