i. Only Reshiram and Ninetales benefit from Drought; if you want to have a sun team, then build it around the weather type.
ii. I personally wouldn't use Choice Specs on Reshiram, but use a Flame Charge speed boost set (Reshiram's attack is irrelevant for Flame Charge since you want the speed boost and are not really concerned with the damage dealt).
iii. That's a horrible set for Mienshao. It's way too frail to set anything up, it has no reliable method of recovery that a set up Pokemon needs, and it has much better potential as a Life Orb/ Choice Scarf sweeper.
iv. There is no point in giving Deoxys-Attack a low power move like Knock Off; that's a move for walls like Deoxys-Defence. Give it Hidden Power Fire and Extreme Speed in replacement of Knock Off and Recover (it has no time to recover because its defences are so low that if you let your opponent do anything to you it will be KO'd). Also, make its nature Naive. It doesn't matter if Naive lowers its Sp. Def, since it's so low anyway it won't make a difference.
v.Give Zekrom Choice Scarf instead so it has a better chance of outspeeding a Kyogre, they usually carry Ice Beam. Thunder is a rubbish move unless you're facing a Rain Team, and since Zekrom is a physical attacker there's no need for it (it has Bolt Strike already). I don't understand why you gave it a Choice Band when you gave it 3 special moves.
vi. Blizzard is the same as Thunder; without its weather type (Hail) it's a rubbish move at an accuracy of 70%. Again, mixed sweepers shouldn't have neutral natures; sweepers aim to get rid of their opponents as soon as possible, so it's not as if you'd be taking too many hits. And finally, why did you give a Choice Scarf Pokemon Roost?
I don't think you fully understand Kyurem using Draco Meteor; if you have Kyurem in and it uses Draco Meteor, it can only use Draco Meteor until you switch it out, meaning having a physical move is pointless since you can't use it. When a Pokemon is switched out its stats reset to normal, meaning the sp. atk drop from Draco Meteor is negated and Kyurem's sp. atk goes back to normal.
3 of your 6 Pokemon have a x2 Rock weakness, and you don't have a Rapid Spinner.
3 of your 6 Pokemon have a x2 Dragon Weakness, and you have no wall to switch in and take hits.
3 of your 6 Pokemon are Choiced, which means that half of your team is constantly locked into one move.
4 out of 6 of your Pokemon are Uber, so why do you have Ninetales instead of Groudon? Mienshao can act as a fast sweeper, but it's best suited to OU rather than Ubers.
Reshiram @ Leftovers
EVs: 252 Speed, 252 Sp. Atk
Zekrom @ Choice Scarf
EVs: 252 Speed, 252 Sp. Atk
Note that with Volt Switch, Zekrom can act as a scout and switch out quickly to a more favourable Pokemon.
Deoxys-A @ Life Orb/ Focus Sash
EVs: 252 Sp. Atk, 252 Speed, 4 HP
Focus Sash will mean that you can hang on and keep sweeping. To be honest, Deoxys-A doesn't really need Life Orb, but it's your choice.
Kyruem @ Life Orb
EVs: 252 Speed, 232 Sp. Atk, 24 Atk
Dragon Claw/ Earth Power
Kyurem's attack is high enough without that you don't need that much EV investment, and since it doesn't drop from anything, it can afford to put most of its EVs in Sp. Atk.
If you really wanted a sun team, then:
Groudon @ Leftovers
EVs: 252 HP, 252 Def, 4 Atk
If you really wanted to use Mienshao:
Mienshao @ Life Orb
EVs: 252 Atk, 252 Speed, 4 Sp. Atk
Forretress @ Leftovers
EVs: 252 HP, 252 Sp. Def, 4 Def
Blissey @ Leftovers
Ability: Natural Cure
EVs: 252 Def, 252 Sp. Def, 4 HP
Completely susceptible to Taunt, but eh, it's Blissey.
Lugia @ Leftovers
EVs: 252 HP, 176 Def, 80 Sp. Def