Before I start my rate, my I say that Anti is correct that Flygon requires Adamant to be an effective Choice Bander. The main reasons you'd use Flygon over something like Salamence include Flygon's Stealth Rock resistance, U-Turn, and of course, the STAB Earthquake. Almost everything else, including Specs, Mixed, Bulky, etc...are done
better by Salamence. Salamence has a lot more power, more than 100 points of Attack when factoring in Adamant and a Choice Band. Still, this team needs something to come in and automatically cause a problem without any consequences. Salamence can do the same thing, but the lack of a Rapid Spinner on this team means Stealth Rock eats up 25% of its health. Flygon is superb for opening up sweeps, and softening the oppositions team.
That aside, I hope you're leading with Hippowdon, because if you're not, your lead Flygon will be dying a lot quicker to Azelf and Infernape. Sure he can break their sash, but both outspeed and can either OHKO (Explosion on Azelf, Fake Out + Endeavor + Vacuum Wave on Infernape). Hippowdon breaks their sash, and can Roar them both out, or just set up his own rocks. With an established lead, I must say, Swords Dance is the better option. Sometimes, the Baton Passes don't work. I can name a few scenarios where Leafeon would be successful with something else such as Wishpassing. I'd personally use something like this:
Leafeon @ Leftovers
Impish
252 HP / 114 Def / 144 Spe
-Leaf Blade
-Wish
-Roar
-Protect / Knock Off
Maximum HP and 114 Defense EVs grants 334 HP / 356 Defense. 144 Speed EVs allows you to outrun Adamant Gyarados, Jolly Tyranitar, and anything below. Wish and Protect are standard, and aid with handling Gyarados (whom can deal 70% maximum with Ice Fang, so be careful). If you come in quickly, you can Roar it out, or kill a weakened Gyarados with Leaf Blade. You could also go Maximum HP and Maximum Defense, to better take hits, but you now fail to outrun Adamant Gyarados and Jolly Tyranitar.
Use Aromatherapy on Vileplume. It's the only thing keeping it different from things like Venusaur and Tangrowth. Other than that, nothing else really. DD Tyranitar is troublesome, as is MixMence, as you have no safe switch in, nor a reliable way to kill it outside of Starmie, who could die to a CB Pursuit. Among other things, this team has trouble with hard core Special Attacks. Things like Specs Jolteon is a real ass to this team, as are SubGar (Sub / Focus Blast / Shadow Ball / Hypnosis or Thunderbolt). You could try a Special Wall, or even a Tank like Snorlax. I don't know, it's your team.
EDIT
Notice I said threats like Jolly Lucario. His team has no answers for Salamence, Zapdos, in fact anything with mediocre power over base 100 gives this team intense trouble. Salamence absolutely crushes this team after 1 DD as nothing can switch into it. Zapdos is unresisted, so having it can just OHKO half your members and 2HKO your walls. I would think that you would want atleast a way to attempt to stop them.
Salamence is a huge problem, as is Zapdos. However, I disagree with DD Mence destroying this team. Hippowdon is the best check today for it, although sims using Yawn is just idiotic. Ice Fang or Roar are much better alternatives. Ice Fang if he uses my Leafeon (=]).
Have you noticed why no one uses Jolly Flygon? Because it has basically the same % as CB Flygon, which no one runs. Adamant is for Scarf which is extremely useful, Jolly is for Choice Band, and Naughty is for Life Orb. About 1/5th of the people who run CB run Adamant, so obviously that is saying something about collective opinion and knowledge.
I don't listen to statistics all the time, since there are many stupid people laddering everywhere. Adamant is the superior nature for this team, which doesn't have a lot of offensive power whatsoever. Thus, the extra power supplied by Adamant is superior in this case.
You mentioned Cresselia as the need for power. This I actually lol at because if Cresselia can take Salamence with grace,
2HKOed by CB Outrage 100% of the time when factoring in SR. 2HKOed by DD LO Outrage 100% of the time, regardless of SR or not. 2HKOed by Specs Draco Meteor when SR is down. Cresselia is a very shaky answer to Mence.
it can most certainly take Flygon just as easily.
Fair enough. U-Turning still is very annoying, especially with no Leftovers thanks to Sandstorm. Flygon can come out on top with enough prior damage, but yeah, Cresselia forces Flygon out in early game.
You still have yet to show any hard evidence of anything common that can be prevented by increasing the attack power. The only arguement so far is that it will 2HKO the non-threatening Swampert which I found anyways. If you can list things that it will now for sure OHKO or 2HKO (and outrun) with the attack boost you would have a stronger arguement. For now you are simply saying attack > speed because this team itself lacks power.
Vaporeon at times is not 2HKOed by Outrage from a Jolly specimen. That's important, since Vaporeon has the strongest bulky water Ice Beam in OU. Outrage loses a lot of power besides that, for example, Flygon can't 2HKO Porygon2 100% if Jolly. With Adamant, Flygon has a small, yet existing chance to 2HKO Shed Shell Skarmory with Stealth Rock down with Fire Punch. There is no such chance with Jolly. Flygon 2HKOs Suicune 100% of the time with Stealth Rock, but with Jolly, the chance lowers to 35%.
This does not give the lead which can be OHKO'd quite easily by common leads the right to sacrifice its speed for the extra boost if it will not be around to supply the power. Flygon without Fire Blast/Draco Meteor cannot break walls btw as it cannont hit from the special side.
Flygon should not be using Draco Meteor. It sucks coming off its Base 80 Special Attack. Fire Blast is good on the Scarf set, for Skarmory and Forretress. Otherwise, on CBer, Fire Punch is superior. I agree with your last point though.
@ OP: Once again, Outrage Flygon is completely outclassed by Salamence.
Earthquake Salamence is completely outclassed by Flygon.
@ There is no point is using Flygon if you are using it for Outrage. You are basically saying you want to use Altaria instead of Salamence because it looks bulkier, has DD as well, and has Natural Cure.
False statement. The Stealth Rock weakness and resistance can play a major role in what switches in and what does not switch in. And Altaria can be used over Salamence. It's not a smart idea whatsoever, since Altaria has the same weaknesses, same SR weakness, and only has Natural Cure to offer over Mence and a little bit of special bulk.
@ Just because it has better resistances does NOT make it a better user of Outrage. Not using a poke that is clearly outclassed by another just because 'it doesn't work for you' isn't really a reason. You can do it, but seeing as you are using a poke that is completely overshadowed, I don't see your reasoning.
Outrage is not the only move on the set. Once you realize that, then maybe I can better understand where you're coming from.