Giving natures for each Pokemon would be helpful. There's also no such thing as a mixed-tier team because if you use an OU Pokemon with a bunch of UU and below Pokemon, it's considered OU by default.
Placing all of Ferrothorn's EVs into both its defenses is a waste of bulk. Maxing out HP first before going for defenses is the best way to EV defensive Pokemon. The preferred EV spread is 252 HP/88 Def/168 SDef with a Relaxed nature. Gyro Ball and Power Whip are also Ferrothorn's preferred STAB attacks, as both pack more power than Iron Head (the former moreso given how horribly slow Ferrothorn is):
-Stealth Rock/Spikes
-Leech Seed
-Power Whip/Protect
-Gyro Ball/Thunder Wave
Nature: Relaxed
EVs: 252 HP/88 Def/168 SDef
Item: Leftovers/Shed Shell
Ability: Iron Barbs
Chandelure has merit, but it's not that fast and is weak to Stealth Rock. Fire Blast is preferred over Flamethrower for the raw power while still having acceptable accuracy, while Overheat can also be used for a powerful nuke; the Special Attack drop isn't much of a problem, since Choiced Pokemon switch in and out a lot:
-Fire Blast/Overheat
-Shadow Ball
-Hidden Power (Fighting)/Ice
-Trick/Energy Ball
Nature: Modest/Timid
EVs: 4 Def/252 SAtk/252 Spe
Item: Choice Scarf
Ability: Flash Fire/Infiltrator
Espeon is outclassed by other offensive Psychic Pokemon because of its shallow move pool. Latios, (Mega) Alakazam, Gothitelle, Mega Gardevoir, Mega Gallade (it's also better than Hitmonlee), Starmie and Mega Metagross are better options over it.
Latios:
-Draco Meteor
-Psyshock
-Surf/Hidden Power (Fire)/Earthquake
-Defog/Roost/Recover
Nature: Timid/Hasty
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb
or
-Draco Meteor
-Psyshock
-Defog/Tailwind/Hidden Power (Fire)
-Trick
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Choice Scarf
Alakazam:
-Psychic
-Shadow Ball
-Focus Blast
-Thunder Wave/Protect/Substitute/Dazzling Gleam/Hidden Power (Fire/Ice)
Nature: Timid
EVs: 4 HP/252 SAtk/252 Spe
Item: Alakazite/Focus Sash
Ability: Magic Guard
Gothitelle:
-Psychic/Psyshock
-Thunderbolt
-Hidden Power (Fire)/Energy Ball
-Trick
Nature: Modest
EVs: 172 HP/252 SAtk/84 Spe
Item: Choice Specs
Ability: Shadow Tag
Gardevoir:
-Psyshock
-Hyper Voice
-Focus Blast
-Taunt/Will-o-Wisp/Substitute/Calm Mind
Nature: Timid/Modest
EVs: 24 Def/232 SAtk/252 Spe
Item: Gardevoirite
Ability: Trace
Gallade:
-Swords Dance
-Close Combat
-Zen Headbutt
-Knock Off/Ice Punch
Nature: Jolly
EVs: 252 Atk/4 Def/252 Spe
Item: Galladite
Starmie:
-Scald
-Rapid Spin
-Reflect Type
-Recover
Nature: Timid
EVs: 248 HP/24 Def/236 Spe
Item: Leftovers
Ability: Natural Cure
or
-Hydro Pump
-Psyshock/Thunderbolt
-Ice Beam
-Rapid Spin
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb
Ability: Natural Cure
Metagross:
-Meteor Mash
-Zen Headbutt
-Ice Punch/Thunder Punch/Bullet Punch
-Hammer Arm/Earthquake
Nature: Jolly
EVs: 252 Atk/4 Def/252 Spe
Item: Metagrossite
Ability: Clear Body
or
-Agility
-Meteor Mash
-Zen Headbutt
-Hammer Arm/Earthquake/Ice Punch
Nature: Adamant
EVs: 80 HP/252 Atk/176 Spe
Item: Metagrossite
Ability: Clear Body
Ice Beam has redundant coverage with Goodra's Dragon STAB. Here's a better way to use Assault Vest Goodra:
-Draco Meteor
-Fire Blast
-Thunderbolt/Sludge Wave/Sludge Bomb
-Earthquake/Muddy Water
Nature: Modest
EVs: 240 HP/252 SAtk/16 Spe
Item: Assault Vest
Ability: Sap Sipper
The preferred nature and EV spread for Gliscor is 252 HP/56 Def/200 Spe to outspeed Adamant Excadrill.
Hitmonlee has little merit in OU teams because of its physical frailty and susceptibility to priority. If you didn't opt for Mega Gardevoir, Mega Gallade, or Mega Metagross, Mega Lopunny is the speedy Fighting Pokemon to turn to:
-Fake Out
-Return
-High Jump Kick
-Ice Punch/Healing Wish/Toxic
Nature: Jolly
EVs: 252 Atk/4 Def/252 Spe
Item: Lopunnite
Ability: Limber
or
-Substitute
-Return
-High Jump Kick
-Baton Pass/Ice Punch/Encore
Nature: Jolly
EVs: 252 Atk/4 Def/252 Spe
Item: Lopunnite
Ability: Limber
If you did opt for the Megas I mentioned over Lopunny, Terrakion and Breloom are alternatives. Hawlucha is also a better Unburden abuser thanks to its access to Swords Dance and higher Speed:
Terrakion:
-Stealth Rock
-Stone Edge
-Close Combat
-Taunt
Nature: Jolly
EVs: 252 Atk/4 Def/252 Spe
Item: Focus Sash
or
-Swords Dance
-Stone Edge
-Close Combat
-Quick Attack/Substitute
Nature: Jolly
EVs: 252 Atk/4 SDef/252 Spe
Item: Life Orb/Salac Berry
or
-Stone Edge
-Close Combat
-Iron Head
-Rock Slide/X-Scissor
Nature: Jolly/Adamant
EVs: 252 Atk/4 SDef/252 Spe
Item: Choice Scarf
or
-Stone Edge
-Close Combat
-Quick Attack
-X-Scissor/Rock Slide/Toxic
Nature: Jolly
EVs: 252 Atk/4 SDef/252 Spe
Item: Choice Band
Breloom:
-Bullet Seed
-Mach Punch
-Rock Tomb
-Spore
Nature: Jolly/Adamant
EVs: 252 Atk/4 Def/252 Spe
Item: Life Orb/Focus Sash
Ability: Technician
Hawlucha:
-Swords Dance
-High Jump Kick
-Acrobatics
-Substitute
Nature: Jolly
EVs: 12 HP/252 Atk/244 Spe
Item: Sitrus Berry
Ability: Unburden