Okay. From the QC meeting on Sunday, we have a list of changes that need to be made in this analysis.
Set 1
First of all, Leftovers is the standard, and best, item on this set. It grants Thundurus a great deal of longevity that allows it to persevere throughout the battle MUCH more easily. Life Orb is indeed good for the extra power, so it should absolutely be slashed, but Leftovers / Life Orb, no doubt.
Also, Thunderbolt and HP Ice are staple attacks. Nothing should be slashed with them. The set should be Thunder Wave | Thunderbolt | Hidden Power Ice | Focus Blast / U-turn. Hidden Power Flying should be mentioned in Set Details for use over HP Ice, in addition to Substitute and Taunt for the last slot.
Set 2
First, unslash Lum. It doesn't really have much application (unless you're into blocking Spores or something idk ?_?) on Thundurus, a Pokemon that isn't physical or particularly hurt by Toxic. Leftovers should be slashed in its place, granting Thundurus, again, a great deal more longevity. This is particularly significant because NP has to actually get up boosts, and Lefties makes it way harder to wear down. Also, Taunt just doesn't seem like that great of an option, which we all agreed on. Slash Substitute instead. It protects Thundurus from priority and Scarfer RKs which is very useful, and overall makes it more difficult to deal with. Finally, HP Flying should be slashed with HP Ice. It is a very good option to take out Mega Venusaur, a top-tier defensive threat. The set should be Nasty Plot | Thunderbolt | Hidden Power Ice / Hidden Power Flying | Focus Blast / Substitute, Life Orb / Leftovers.
Set 3
This set is kinda weird the way it is right now. What it should look like is this:
Mixed
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name: Mixed
move 1: Thunderbolt
move 2: Knock Off
move 3: Superpower
move 4: Hidden Power Ice / U-turn / Taunt
ability: Defiant
item: Life Orb
evs: 72 Atk / 180 SpA / 252 Spe
nature: Naive
Thunderbolt is mandatory. Knock Off is mandatory for the Latis, Aegislash, and crippling defensive answers to Thundurus in general. Superpower is mandatory for Tyranitar, Chansey, and Heatran. The last slot is a toss-up of what you want. HP Ice is generally best because it destroys Gliscor, Landorus-T, and Garchomp. U-turn is also good because, well, it's U-turn (momentum and such). Finally, Taunt prevents Pokemon like Chansey, non-Rock Slide (aka most) Hippowdon, and Gliscor from doing much of anything to Thundurus while it just does whatever it wants and proceeds to switch out.
The Attack EVs let Thundurus KO Latios with Knock Off after SR.
Set 4
Remove this set. With Sub and Taunt mentioned in the first set, its role is entirely encompassed by the other sets. Thus, there is no reason to have this set.
Add this set:
Bulk Up
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name: Bulk Up
move 1: Bulk Up
move 2: Fly
move 3: Wild Charge
move 4: Superpower
ability: Defiant
item: Power Herb / Leftovers
evs: 4 HP / 252 Atk / 252 Spe
nature: Jolly
Bulk Up Thundurus has been a recent innovation as an excellent Mega Venusaur lure. Power Herb Fly means Mega Venu will be totally surprised; Leftovers is an option because Fly gives you recovery in the air, and not much wants to switch into a boosted Fly that wouldn't beat Thundurus anyways. Wild Charge is the other obligatory STAB, and Superpower provides coverage on annoying things like Tyranitar and Heatran that would otherwise seriously hinder Thundurus. There's unanimous agreement that this set should be included, btw.
Potentially add this set:
Defiant
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name: Defiant
move 1: Wild Charge
move 2: Knock Off
move 3: Superpower
move 4: U-turn / Fly
ability: Defiant
item: Life Orb
evs: 4 HP / 252 Atk / 252 Spe
nature: Jolly
I was talking to dragonuser on IRC, and realized I definitely wasn't the only one having positive experiences with all-out physical Thundurus. This is a Pokemon specifically meant for Deoxys hyper offense teams, as it can take massive advantage of Defog with Defiant. Thundurus's impressive base 115 Attack stat makes its physical attacks hit hard; with a Defiant boost, it becomes quite the hard hitter offensively. It can throw around Knock Offs, which murder the Latis (even OHKOing Latias thanks to the physical bias of this set) and generally greatly cripple defensive switch-ins to Thundurus. Wild Charge is STAB, Superpower is coverage...and then there's the last slot. U-turn is really good because momentum move and all that jazz, but Fly is also nice because of Mega Venusaur, which Thundurus attracts like a dog does fleas. This set has been proven in SPL and by various users on the ladder as a nice option for Thundurus to run.