Hello, now that you've adjusted your overall team to better suit the current metagame, might I offer up a few more suggestions?
Right now, you've said your line up is as follows:
1. LO Hydregion, Mixed
2. Ferrothorn, Standard
3. Mienshao, LO, All out Attacker
4. Latios, Offensive LO
5. Thundurus-T, Nasty Plot
6. Volcarona, Sub-Quiver
I have a few thoughts about the team's overall synergy, and its place in the OU metagame.
The first big, glaring error is that you have Volcarona without a Spinner. Once your opponent lays down Stealth Rocks (And they will), your Volcarona is essentially worthless. With the diverse movepools, mighty stats, and multiple strategies of the OU metagame, a Volcarona with half of its HP is easy-to-kill deadweight. This will lead into my next point.
Secondly, I feel like your team is very unbalanced in a bad way. Don't get me wrong, there's nothing wrong with a Heavy Offensive team (Especially with Ferrothorn as a Defensive pivot), but your Pokemon choices lack the necessary raw destructive power that a Heavy Offensive team needs. Looking at it you have A defensive wall leaning on the Sp. Def side, one UU Physical Attacker, and 4 Special Attackers (Yes, the Hydregion is mixed, but frankly, Mixed Hydregion is very underwhelming. Salamence and Dragonite do it better).
Lastly, your team is rather weak as a whole to some of OUs major threats, and a few of the Anti-Metagame surprises that pop up every now and then to ruin everyone's day. Tyranitar, Terrakion, Landorus, and Infernape are all Pokemon that will give this team problems. Ferrothorn presents a weak counter to the increasingly popular Mixed T-Tar, while Latios and Hydregion don't provide the proper challenge to it with its boosted Sp. Def in the sand. A Scarfed Terrakion would ram through Close Combat for your first three Pokemon, an X-Scissor for Latios, and Stone Edge for the last two. You'd run into the same problem with Scarfed Landorus, scoring Super Effective hits on all your Pokemon with just a few simple switches. Infernape isn't as glaring a problem with Latios, but still gives the rest of your team a scare with a standard mixed set.
Therefore, to alleviate these aforementioned problems, here's what I suggest:
Replace Hydregion with Donphan. While it may not be the best Defensive wall, it creates synergy well with the rest of the team. Also, it provides three key elements to the table: Stealth Rocks, A Defensive Wall, and Rapid Spin. The standard set should suffice:
Donphan @ Leftovers
Ability: Sturdy
EVs: 252 HP / 4 Atk / 252 Def
Impish Nature
- Rapid Spin
- Stealth Rocks
- Earthquake
- Toxic/Roar/Knock Off
Secondly, I'm sorry but Mienshao has got to go. I would go with Platinum Dude's great suggestion of Breloom, who with the upcoming release of Technician, is going to become a fierce new competitor in the OU metagame. His set was fantastic:
Breloom @ Life Orb
Ability: Technician
EVs: 4 HP / 252 Atk / 252 Spe
Nature: Adamant
- Spore
- Mach Punch
- Bullet Seed
- Stone Edge/Swords Dance
I would opt for Stone Edge for better coverage.
Hope this helped!