Umbreon @ Leftovers
Trait: Synchronize
EVs: 252 Def, 252 Sp. Def, 4 HP
Calm Nature
- Moonlight/ Wish
- Toxic/ Protect
- Heal Bell
- Foul Play
Umbreon will be susceptible to taunt, so look out for that. In any case, Foul Play is the better option for Umbreon because of its low attack and sp. attack stats, since Foul Play will be calculated by the opponent's attack stat.
You can go either Moonlight or Wish; Wish will take one turn to activate, but Moonlight is dependant on weather. Since there is no sun in UU, the usual amount Moonlight will restore is 1/2. However, with Abomasnow dropping to UU, Hail will cause Moonlight restore only 1/3 of Umbreon's HP; make the decision accordingly.
Blastoise @ Leftovers
Trait: Torrent
EVs: 122 SDef / 252 HP / 134 Atk
Careful Nature
- Roar
- Toxic
- Rapid Spin
- Scald
Roar to get rid of calm mind stallers and baton passers, and Scald for burn hax (and drop in attack). Imo there's not much of a need for Aqua Jet on Blastoise. You can replace Toxic with Aqua Jet if you want.
Also, Roar over Dragon Tail because of accuracy, and Dragon Tail does not break a substitute.
Mienshao @ Life Orb
Ability: Regenerator
EVs: 252 Atk, 252 Speed, 4 HP
Nature: Joly
- Fake Out
- U-Turn
- Hi Jump Kick
- Stone Edge
Mienshao is too frail to set up even one swords dance; I guess that's what your focus sash is for, but you need to take into account Pokemon with priority moves. You obviously want it to sweep ASAP, and Life Orb will give it the boost it needs, while Regenerator will give it its HP back.
Or, you can run a choice set.
Mienshao @ Choice Scarf
Ability: Regenerator
EVs: 252 Atk, 252 Speed, 4 HP
Nature: Adamant/ Jolly
- U-Turn
- Drain Punch
- High Jump Kick
- Stone Edge
This way, Meinshao can outspeed most of the tier. Trade off is that it will be locked into one move, but imo Mienshao usually goes out for its STAB Hi-Jump Kick or U-Turns out of a Psychic type. Also, you can send Scarf Mienshao out as your lead, and scout out what the opponent will try to do, then U-Turn out of there.
Victini @ Choice Scarf/ Specs
Ability: Victory Star
EVs: 252 Sp. Atk, 252 Speed, 4 HP
Modest/ Jolly Nature
- Psychic
- Grass Knot
- U-turn
- Overheat/ Blue Flare
Victini can act as a Special attacker as well. However, unless you have an event Victini, it can't learn Blue Flare, so go with Overheat, which is its next most powerful sp. fire move. 90% accuracy is okay, really. Or if you're playing on Showdown, Blue Flare.
Azumarill @ Choice Band/ Life Orb
Ability: Huge Power
EVs: 252 Atk , 4 HP, 252 Spd
Nature: Adamant
- Ice Punch
- Superpower/ Return
- Waterfall
- Aqua Jet
Not much to change here, but I guess Azumarill might favour Return more than Superpower, so it doesn't sacrifice its attack with one move.
Scrafty @ Leftovers
Ability: Shed Skin
EVs: 128 Atk, 128 Def, 252 Sp. def
Nature: Careful
- Rest
- Drain Punch
- Crunch
- Bulk Up
Shed Skin set. It's a rist that Shed Skin won't activate in time, but it's a fun set imo. Bulk Up and then sweep. Simple enough.
OR
Scrafty @ Lum Berry
Ability: Moxie
EVs: 252 Atk, 252 Speed, 4 HP
- Dragon Dance
- Drain Punch
- Crunch
- Ice Punch
This is the more common Scrafty set. Lum Berry is to deal with anything that will status you.
I think you could replace Scrafty or Azumarill with another sp. sweeper (since you only have 1 in Victini, and 3 physical sweepers), or maybe a Cleric (now that Chansey is in UU). Going by type disadvantage, I would replace Scrafty. You already have Umbreon to wall Psychic types, and Mienshao's Fighting type.
You can consider something that will set up entry hazards and block Rapid Spinners like Froslass, or another special sweepers like Porygon2 w/ Eviolite, Suicune or Zapdos.
Rubber duck @ Eviolite
Ability: Download/ Analytic
EVs: 252 Sp. Atk, 252 HP, 4 Def
Nature: Modest/ Quiet
- Recover
- Tri Attack
- Ice Beam
- Thunderbolt
Standard set for Porygon2; Analytic is a Life Orb boost without recoil (providing it goes last), or Download in case you actually outspeed something with a base 60 speed.
Suicune @ Leftovers
Ability: Pressure
EVs: 252 Hp, 108 Sp. atk, 144 Sp. def
Nature: Modest
- Rest
- Sleep Talk
- Scald
- Calm Mind/ Ice Beam
Defensive Rest Talk Suicune; it can stall successfully, even with just Scald (if you want to go for calm mind).
Zapdos @ Life Orb
Ability: Pressure
EVs: 252 Sp. Atk, 252 Speed, 4 HP
Nature: Timid
- Thunderbolt
- HP Ice/ Grass
- Heat Wave
- Roost
It's a shame that Zapdos has no good flying moves, but I guess Heat Wave deals with Grass and Ice types at the same time.
Froslass @ Leftovers
Ability: Cursed Body
EVs: 252 HP, 252 Speed, 4 Sp. def
Nature:
- Taunt
- Spikes
- Pain Split/ Destiny Bond
- Ice Beam/ Shadow Ball
Frosslass is quick enough to set up Destiny Bond to take something down with it. Taunt is there to prevent other set ups, and Ice Beam/ Shadow Ball covers its own Taunt liability.