Competitive team for battling online.

Hey all! I'd appreciate some input on a team I've put together. This is my first team ever, so if I've made any rookie mistakes, please point them out! The team is:

Gardevoir @ Gardevoirite
Nature: Modest
Ability: Trace > Pixilate
EVs: 252 Sp. Att, 252 Speed, 4 HP
Moves: Moonblast/Hyper Beam, Focus Blast, Psyshock, Shadow Ball
Gardevoir is the bread and butter of my team, able to reliably take down a huge array of opponents.

Aegislash @ Leftovers
Nature: Brave
Ability: Stance Change
EVs: 252 HP, 204 Att, 52 Sp. Def
Moves: King's Shield, Shadow Claw, Iron Head, Swords Dance
Aegislash is my main tank on the team. Swords Dance gets him buff while opponents try to kill him, and then he sweeps.

Rotom @ Leftovers
Nature: Modest
Ability: Levitate
EVs: 252 HP, 128 Def, 128 Sp. Def
Moves: Volt Switch, Hydro Pump, Will-O-Wisp, Pain Split
This Rotom can scout other Pokemon and is able to apply burn via Will-O-Wisp. Pain Split can be used on full health slow Pokemon (when Rotom is only moderate or less) to recover health and deal damage at the same time.

Tyranitar @ Assault Vest
Nature: Adamant
Ability: Sand Stream
EVs: 252 HP, 252 Sp. Def, 4 Att
Moves: Crunch, Earthquake, Stone Edge, Thunder Punch
Assault Vest + EVs allows T-tar to become very tanky. His base attack isn't bad at all, so he benefits from physical attacks. In the end, he's able to tank out attacks and deal some serious damage.

Skarmory @ Rocky Helmet
Nature: Impish
Ability: Sturdy
EVs: 252 HP, 252 Def, 4 Speed
Moves: Spikes, Roost, Whirlwind, Brave Bird
Skarmory makes a very nice physical wall and hazard set-up(per?). Brave Bird lets Skar take care of those pesky Fighting types that are ever-so-dangerous for my team.

Landorus-Therian @ Leftovers (yes I know, Leftovers everywhere...)
Nature: Impish
Ability: Intimidate
EVs: 252 HP, 248 Def, 8 Speed
Moves: U-Turn, Stealth Rock, Stone Edge, Earthquake
Landorus-T has ridiculous base attack. I basically switch him into a match-up that forces the opponent to switch out with another mon. I then set up Stealth Rock, and if Spikes are up too, can deal hefty damage to the enemy switching in. Landorus-T sweeps, and in an ideal world, can use U-Turn to counteract an enemy switch in so I begin the next turn having the upper hand.

I think my team is super defensive, especially physically. Skarmory was added last to the team as it didn't expose my team to new weaknesses and it also gave me the chance to put in a Whirlwind on the team. Let me know what you think!

Is this team for Battle Spot?

Pixilate is pointless when Mega Gardevoir doesn't have moves to take advantage of it. For the record, this ability only affects Normal type moves and doesn't affect moves that are already Fairy type, like Moonblast. Hyper Beam is a bad attack because of the recharge turn after using it. This doesn't help, considering Mega Gardevoir's physical frailty. The most reliable Special Normal attack Gardevoir learns is Hyper Voice, which is decently strong and benefits from Pixilate. 24 Defense EVs should be run on Mega Gardevoir so it can take 2 Psyshocks from Latios. It also doesn't really need Shadow Ball, as Psychic/Fairy/Fighting coverage is good. Tl;dr:
-Psyshock
-Hyper Voice
-Focus Blast
-Taunt/Will-o-Wisp/Calm Mind
Nature: Timid/Modest
EVs: 24 Def/232 SAtk/252 Spe
Item: Gardevoirite
Ability: Trace

What purpose does Aegislash's EVs serve? Swords Dance + King's Shield, while tempting, isn't good, IMO, because this leaves Aegislash easily crippled by burn. Special Aegislash is generally better because it doesn't get crippled by burn as easily:
-Shadow Ball
-Flash Cannon/Sacred Sword
-Shadow Sneak
-King's Shield
Nature: Quiet
EVs: 252 HP/252 SAtk/4 SDef
Item: Leftovers/Weakness Policy

or
-Substitute
-Toxic
-King's Shield
-Shadow Ball/Flash Cannon
Nature: Modest/Timid
EVs: 252 HP/252 SAtk/4 Spe (Modest) or 252 HP/4 SDef/252 Spe (Timid)
Item: Leftovers

or
-Iron Head/Shadow Claw
-Shadow Sneak
-Sacred Sword
-King's Shield/Swords Dance
Nature: Adamant/Brave
EVs: 252 HP/252 Atk/4 SDef
Item: Life Orb/Weakness Policy

What's the point of Wash Rotom having a Modest nature when its Special Attack isn't being invested in? It's better off going fully physically defensive to easily take on physical attackers like Talonflame:
-Volt Switch/Thunderbolt
-Hydro Pump
-Will-o-Wisp
-Rest/Pain Split/Thunderbolt
Nature: Bold
EVs: 252 HP/252 Def/4 SDef
Item: Chesto Berry/Leftovers/Sitrus Berry

Assault Vest seems tempting on Tyranitar, but its common weaknesses make this set kind of difficult to pull off. Better Assault Vest users are Azumarill and Conkeldurr, as the former has a better defensive typing, while the latter's Special Defense can be easily compensated for with its high HP:

Azumarill:
-Waterfall
-Aqua Jet
-Play Rough
-Superpower/Knock Off
Nature: Adamant
EVs: 240 HP/252 Atk/16 SDef
Item: Assault Vest
Ability: Huge Power

Conkeldurr:
-Drain Punch
-Mach Punch
-Knock Off
-Ice Punch/Stone Edge
Nature: Adamant
EVs: 252 Atk/236 SDef/20 Spe
Item: Assault Vest
Ability: Guts

Thanks so much!
I can see why Hyper Voice is actually a good choice (especially now Gen 6 has the corresponding tutor).
For Rotom-W, I just remember reading somewhere that modest nature is better so that it can retaliate harder.
Both Azumarill and Conkeldurr sound good for my team. I'll see which one works better. Thank you again for helping me out :)