Why can't we just give this set a mention in the additional comments of the onsite classic mixed sweeper, because this is set is extremely similar to the one onsite barring Outrage and a different EV spread.
Also, with the BW2 move tutors being released the mixed set is likely to get revamped anyway so we can revisit this issue then.
Really late reply, but other QC members have agreed to at least rework it since the spread on-site seems to be somewhat sub-optimal...
Anyway, I've recently restarted testing now that BW2 madness has settled down somewhat, and have started crunching some calculations to figure out exactly what each variation of this set loses and gains. This has turned out to be a pretty daunting task since there are like 6 variations of this set between varying EV spreads and moves.
The gist of what I have determined is this:
First I took a look to see exactly what I was outspeeding with those speed EVs except for Gliscor. Here's a list of notables and how they can threaten Dragonite:
Uninvested Gyarados (I guess Stone Edge?)
All unboosted Gorebyss (Frequently carries Ice Beam)
Max speed Tangrowth out of Sun (ok that's a stretch, how often do you see that)
Uninvested Suicune and Toxicroak (Ice attack carriers, especially Toxicroak)
Roserade (Sleep Powder and HP Ice)
Sub-Charge Magnezone (Just hits fucking hard)
Max Max Speed Scrafty (Ice Punch)
Modest Specs Politoed (ICE BEAM! Big deal this one)
Standard Tentacruel (Ice Beam, Toxic Sub-tect stall)
Max Speed Tyranitar (Stone Edge)
Bulky Rotom-A (Will-o-wisp, HP Ice)
SD Gliscor (Ice Fang, duh)
Defensive Celebi (HP Ice, T-wave)
Defensive Zapdos (HP Ice, Toxic)
Speed ties with Tormentran (Ok who uses this but yeah I guess)
Then I had to determine if Extreme Speed could beat these threats. The answer is interesting; if we're talking about them switching into an attack from Dragonite, then you can (assuming they didn't switch into a resisted move). But if they come in after a kill, then the answer is a resounding no for almost all of them. So what I find is that interestingly, what we thought was giving Dragonite staying power (kill revenge killers) actually lets MORE Pokemon revenge kill it. And don't assume prior damage, since this set isn't a clean up sweeper, it's a wallbreaker. It usually shows up pretty early in the game, so you can't expect more than 20% prior damage on anything.
So really, the only benefit from using the old spread is you get a decent priority move. It greatly detracts from the wallbreaking purpose though, as you lose the coverage from your second physical move.
I suppose the old spread still has some merit if you're desperately looking for more priority on your team, but overall I believe that IT should be the AC mention, not the set I devised.
Quite importantly I discovered that now that Multiscale and Superpower are compatible that it is without a doubt the best move in the third slot under most circumstances.
Now onto a different topic; Outrage and just how necessary it is. When playing with this set recently I've found myself using Outrage very little for one key reason; clicking it pretty much ensures your death unless you've eliminated everything that can threaten Dragonite already. This, combined with the fact that running both Superpower and EQ is entirely feasible, made me wonder just how necessary Outrage really was.
Ultimately, I discovered that Outrage does help nab a couple key KOs that EQ doesn't. The most prominent one is Jellicent, who you cannot 2HKO with Draco-Meteor without significant prior damage. Specially Defensive is KO'd by DM followed by Super Power most of the time, but can survive. With Outrage, it cannot. Against other mons that could feasibly take two Draco meteors though, it proves much less useful. Obviously against Steels you're better off with EQ, Fire Blast or Super Power. Defensive Politoed is 2HKO'd by Draco meteor followed by Superpower. Chansey is 2HKO'd by Super-power much more reliably so it's a non-issue. Tentacruel is hit harder by EQ. Porygon2 is hit harder by Superpower as well.
So I'm thinking that in most circumstances EQ is actually better than Outrage, primarily since this way if you mis-predict you didn't just waste Dragonite. Even Jellicent and Politoed will fall with a bit of prior damage, and Dragonite's main role is to take out Physically defensive Pokemon anyway, not specially defensive ones.
Finally, I had one more thought; Do I really need an attack boosting nature, or is a SpA boosting nature better? Basically, the physical attacks are there purely to nab specific KOs, if the boost doesn't make a difference to those KOs then I might as well boost my main attacking moves in Fire Blast and Draco meteor.
My first calculation was the obvious one; Chansey. I discover that it does in fact make a difference; what was originally a guaranteed 2HKO is now possible to miss out on without SR. Still, that's fairly minor as you just need to NICK Chansey to secure it. I then check some others. Jirachi comes first, and I find that it makes no significant difference. Tentacruel and Tyranitar are mostly the same as well. Porygon2 becomes slightly harder to crack, but you're losing most of the time to it anyway so that hardly matters. It makes no difference against Blissey. Jellicent is still beaten with Outrage from full health 98% of the time. Without Outrage, Ultility counter Jellicent is 2HKO'd most of the time by Draco Meteor (guaruanteed with SR) while Specially defensive Jellicent is just as hard as it was before. So, Bold Jellicent is easier to beat with Rash. Politoed also becomes easier, becoming a guaranteed 2HKO with Draco Meteor, meaning you don't have to lower your Defense and Attack to take it out. Gastrodon is exactly the same as before.
So, for the tl;dr people, what I have concluded is this;
-Extreme Speed is useless unless you REALLY want priority, use my spread.
-Outrage is outclassed by SP and EQ except against Specialyl defensive Jellicent
-Rash or other SpA boosting nature is better than Attack boosting nature 99% of the time.
So, the new standard set would look like:
Dragonite @ Life Orb
Ability: Multiscale
EVs: 60 Att / 252 SpA / 196 Spe
Nature: Rash
Moves:
-Draco Meteor
-Fire Blast
-Superpower
-Earthquake / ExtremeSpeed (if you're desperate for priority).
Any thoughts, comments, corrections etc. appreciated.