Seismitoad is outclassed by a lot of things in OU. It's only good in rain teams. Gastrodon is the better alternative for its ability to check Water Pokemon:
-Earthquake/Earth Power
-Scald
-Toxic/Ice Beam
-Recover
Nature: Relaxed/Bold
EVs: 252 HP/252 Def/4 SDef
Item: Leftovers
Ability: Storm Drain
or
-Surf
-Earth Power
-Ice Beam
-Recover
Nature: Modest
EVs: 172 HP/84 Def/252 SAtk
Item: Wise Glasses/Mystic Water/Splash Plate
Ability: Storm Drain
If you're using a Quiet nature on Reuniclus, use Trick Room:
-Trick Room
-Psychic/Psyshock
-Shadow Ball
-Focus Blast/Hidden Power (Fire)
Nature: Quiet
EVs: 192 HP/64 Def/252 SAtk
Item: Life Orb/Leftovers
Ability: Magic Guard
Fly is too easily played around on Braviary. Brave Bird is the better option:
-Return
-Brave Bird
-Superpower
-U-turn
Nature: Adamant/Jolly
EVs: 4 HP/252 Atk/252 Spe
Item: Choice Band/Choice Scarf
Ability: Defiant
Eelektross isn't worth using, IMO, despite its good move pool, because of its bad Speed. Wash Rotom is the better fit:
-Volt Switch
-Hydro Pump
-Will-o-Wisp
-Pain Split/Hidden Power (Ice)
Nature: Modest
EVs: 232 HP/56 SAtk/220 Spe
Item: Leftovers
or
-Volt Switch
-Hydro Pump
-Thunder Wave/Will-o-Wisp
-Pain Split
Nature: Calm
EVs: 248 HP/28 SAtk/232 SDef
Item: Leftovers
or
-Volt Switch
-Hydro Pump
-Hidden Power (Ice)
-Trick/Thunderbolt
Nature: Timid
EVs: 4 HP/252 SAtk/252 Spe
Item: Choice Specs/Choice Scarf
Gallade isn't that good in OU because of its middling Speed; Lucario is the better option over it:
-Swords Dance
-Close Combat
-ExtremeSpeed
-Crunch/Ice Punch/Shadow Claw/Bullet Punch
Nature: Adamant/Jolly
EVs: 4 HP/252 Atk/252 Spe
Item: Life Orb