Need help fixing weaknesses in my Team. OU

[Dark T]

I have good success online for the most part; I just feel like I have a lot of weaknesses.

Online Battles:
8BHG-WWWW-WWW3-YDRF - (Opponent used Mega Mewtwo Y)
HHJG-WWWW-WWW3-HAZC
VQUW-WWWW-WWW3-HBPF
T7XW-WWWW-WWW3-7EZ6 - (Last example was with a non Sturdy Aggron.)

Aggron @ Quick Claw
Ability: Sturdy
EVs: 112 HP / 160 Atk / 236 Def
Adamant Nature
- Stealth Rock
- Roar
- Iron Head
- Rock Tomb
My goal with Aggron is to send out his Stealth Rock. I have him as a Sturdy nature to ensure he can at least use the move in a worst case scenario. He knows Roar to force switching into the SR or to remove a Pokemon attempting to set up on him. Rock Tomb and Iron Head are used as STAB attacks with Rock Tomb lowering the opponents speed closer to his own.

Umbreon @ Leftovers
Ability: Synchronize
EVs: 252 HP / 4 Def / 252 Sp. Def
Impish Nature
- Curse
- Payback
- Toxic
- Moonlight
I use my Umbreon to use Curse and hit hard with a powerful STAB Payback. Moonlight allows Umbreon to heal himself as his defence continues to rise and Toxic continues to hurt the opponent. When Umbreon is cursed up well enough he will go in for the kill.

Salamence @ Assault Vest
Ability: Intimidate
Evs: 4 HP / 252 Atk / 252 Spd
Adamant Nature
- Dragon Claw
- Fly
- Crunch
- Earthquake
Taking advantage of a decent speed, Assault Vest, and a high attack, Salamence is meant as a powerful diverse attacker.

Dragonite @ King's Rock
Ability: Multiscale
Evs: 4 HP / 252 Atk / 252 Spd
Adamant Nature
- Dragon Dance
- Waterfall
- Fire Punch
- Thunder Punch
Dragonite fills an elemental void, can endure a good hit at hull HP, and is able to set up a sweep with DD.

Alakazam @ Focus sash
Ability: Magic Guard
EVs: 4 HP / 252 Sp. Atk / 252 Spd
Timid Nature
- Psychic
- Shadow Ball
- Energy Ball
- Dazzling Gleam
Magic Guard is one of the best abilities in the game. It prevents so much annoying damage and works wonderful with Focus Sash. Focus Sash has saved my Alakazam's life so many times. Stubbing his toe is enough to OHKO him so the sash allows for two attacks. Psychic for my STAB damage. Shadow Ball to cover ghosts. Dazzling gleam to cover dark types and is more reliable than Focus Blast. Energy Ball is a good move because of how well it takes care of Rock, Earth, and Water types, many of which are typed together.

Tyranitar @ Tyranitarite
Ability: Sand Stream
EVs: 4 HP / 252 Atk / 252 Spd
Jolly Nature
- Dragon Dance
- Crunch
- Earthquake
- Stone Edge
One of the best members on my team. Dragon Dance makes him an amazing sweeper and incredibly fast. Great bulk allows him to set up the DD, and great attack and speed allows him to out pace and kill many threats.

 

[Dark T]

I am considering possibly replacing Umbreon for a Choice Scarf Chandelure. But there are occassions where his moveset compliments me well and can cripple a team with his bulk/toxic/payback.

I am in the process of getting a Moxie Salamence to replace the intimate one.

 

[Draestrix]

Alright, let's go down this one-by-one:

Aggron: I recommend Leftovers or Rocky Helmet over Quick Claw, which depends too much on chance. Otherwise, I don't know much about running M-Aggron and it looks fine so I'll leave it at that.

Umbreon: Instead of running Toxic, you should run Heal Bell. Why, you ask? Simply because the opponent knows you're going to set up after the first Curse: All he has to do is Toxic you and then your Umbreon's taken a huge hit—walls in general don't like Toxic, especially this variant of Umbreon.

Salamence: Don't run Assault Vest. If you're trying to protect against ice-type moves not even Assault Vest can help much against Salamence's quadruple weakness (also you shouldn't be leaving it in on an incoming ice-type move anyway). I recommend running Choice Scarf or Life Orb to boost damage, because that's really what Salamence is for. As for the moves, there's no reason to use Fly. All it does is give your opponent a free turn to do whatever they want and also flying-type moves aren't great for coverage anyway. I recommend a setup move like Dragon Dance.

Dragonite: King's Rock is not the best item you could be running, for the same reason as Quick Claw—AKA it's too luck-based. Dragonite's also dying for Dragon Claw/Outrage on this set. Also in general Dragonite seems kind of redundant with Salamence. I recommend replacing it with another special sweeper like Greninja, just to throw out a suggestion.

Alakazam: Instead of Dazzling Gleam or Shadow Ball I recommend Focus Blast. It's Alakazam's best way to get past steel types and in general provides better coverage. Otherwise it seems fine.

Tyranitar: seems fine.

 

[Reymedy]

Hello.
Your descriptions are too short to fit the RMT rules requirements.
I encourage you to PM me an updated version of this team with beefed up descriptions, and since you're new, to join the Mentor Program. I'll be unlocking this thread after that.

Have a nice day.