OU Rain Team Help

[flamethrowalrus]

I'm not great at battling, but I'm trying to get better and I wanted to make a team that included Goodra, Heliolisk, and Mega Mawile. It's a rain team, however I think it does a good job not having just water pokemon. Please critique and offer feedback:

Goodra (F) @ Leftovers
Ability: Hydration
EVs: 4 Def / 252 SAtk / 252 SDef
Modest Nature
- Acid Armor
- Outrage
- Rest
- Sleep Talk

Mawile (F) @ Mawilite
Ability: Intimidate
EVs: 252 HP / 252 Atk / 4 SDef
Adamant Nature
- Stone Edge
- Swords Dance
- Play Rough
- Sucker Punch

Swanna (F) @ Damp Rock
Ability: Hydration
EVs: 252 HP / 4 Def / 252 SDef
Calm Nature
- Rain Dance
- Rest
- Tailwind
- Defog

Heliolisk (M) @ Choice Specs
Ability: Dry Skin
EVs: 4 HP / 252 SAtk / 252 Spd
Timid Nature
- Grass Knot
- Surf
- Thunder
- Hidden Power [Ice]

Excadrill (M) @ Air Balloon
Ability: Mold Breaker
EVs: 252 Atk / 4 Def / 252 Spd
Adamant Nature
- Earthquake
- Rapid Spin
- Rock Slide
- Swords Dance

Xatu (M) @ Life Orb
Ability: Magic Bounce
EVs: 32 HP / 252 SAtk / 8 SDef / 216 Spd
Timid Nature
- Psychic
- Grass Knot
- Heat Wave
- Roost

 

[PlatinumDude]

Since rain got nerfed in the generation shift, Hydration isn't as useful as it could be. That and Goodra is walled badly by Fairies:
-Draco Meteor
-Fire Blast/Muddy Water
-Thunderbolt/Earthquake
-Dragon Tail/Earthquake
Nature: Quiet/Sassy
EVs: 248 HP/252 SAtk/8 SDef
Item: Assault Vest
Ability: Gooey/Sap Sipper

or
-Draco Meteor
-Fire Blast/Muddy Water
-Thunderbolt
-Focus Blast
Nature: Modest
EVs: 248 HP/252 SAtk/8 SDef
Item: Choice Specs
Ability: Gooey Sap Sipper

If you insist on keeping Hydration, Hydration wall Goodra should look something like this:
-Dragon Pulse
-Thunder
-Toxic
-Rest
Nature: Calm
EVs: 248 HP/8 Def/252 SDef
Item: Leftovers
Ability: Hydration

Stone Edge doesn't give Mawile noteworthy coverage, apart from Talonflame and Charizard Y, who are hit hard enough by Sucker Punch:
-Play Rough
-Sucker Punch
-Knock Off/Swords Dance/Iron Head
-Substitute/Swords Dance
Nature: Adamant
EVs: 132 HP/252 Atk/124 Spe
Item: Mawilite
Ability: Intimidate

Swanna is very subpar in OU. It has little offensive presence and mediocre defenses. Even with investment, it falls to just about any decently powered move, especially Electric moves. Politoed is pretty much mandatory on rain teams for the setup-free rain:
-Rest
-Sleep Talk
-Scald
-Toxic
Nature: Calm
EVs: 252 HP/4 Def/252 SDef
Item: Damp Rock
Ability: Drizzle

or
-Hydro Pump
-Ice Beam
-Focus Blast
-Hypnosis/Psychic/Scald
Nature: Modest
EVs: 172 HP/252 SAtk/84 Spe
Item: Damp Rock
Ability: Drizzle

If this is a Showdown! team, give Excadrill Iron Head over Swords Dance to smash Fairies with and have a secondary STAB.

Xatu is subpar, tbh. I don't think you need 2 hazard removers, so I think it may be a better idea to include another rain abuser, like Kingdra or Tornadus (either form works):

Kingdra:
-Hydro Pump
-Draco Meteor
-Rain Dance/Outrage
-Waterfall/Surf/Ice Beam
Nature: Rash/Modest
EVs: 64 Atk/252 SAtk/192 Spe
Item: Life Orb
Ability: Swift Swim

or
-Hydro Pump
-Draco Meteor
-Scald
-Ice Beam/Dragon Pulse/Sleep Talk
Nature: Modest
EVs: 24 HP/252 SAtk/232 Spe
Item: Choice Specs
Ability: Swift Swim

Incarnate Tornadus:
-Rain Dance
-Hurricane
-Superpower/Focus Blast
-Taunt/Knock Off
Nature: Naive/Timid
EVs: 4 Atk/252 SAtk/252 Spe
Item: Life Orb/Damp Rock
Ability: Prankster

Therian Tornadus:
-Hurricane/Air Slash
-Superpower/Focus Blast
-Knock Off
-U-turn
Nature: Naive
EVs: 4 Atk/252 SAtk/252 Spe
Item: Life Orb