Countering Terrakion?

Ok, to me he's just another Uber...or at least close to it. It may seem easy to counter it but my team is having trouble countering this guy.
This thing is super strong with speed to match.

I usually go for double battles, so here's my line up:

Mienshao- Adamant, Inner Focus, Focus Sash: 379 Atk, 290 Spd,
-Fake Out
-Rock Slide
-Drain Punch
-U-turn

Whimsicott- Impish, Prankster, Leftovers: 324 HP, 295 Def
-Encore
-Leech Seed
-Taunt
-Substiute

Darmanitan- Adamant, Sheer Force, Life Orb: 383 Atk, 286 Spd
-Superpower
-Flare Blitz
-Rockslide
-U-turn

Sigilyph-Timid, Magic Guard, Flame Orb: 322 HP, 251 Def, 248 Spd
-Stored Power
-Psycho Shift
-Roost
-Cosmic Power

Zoroark-Timid, Illusion, Choice Specs: 320 Spd, 297 Sp Atk
-Night Daze
-Flamethrower
-Grass Knot
-Focus Blast

Haxorus-Adamant, Rivalry, Yache Berry: 418 Atk, 258 Spd
-Rock Slide
-Earthquake
-Outrage
-Dragon Dance

So its not hard to see that my Darmanitan, Haxorus and Zoroark don't have the best IVs. These guys were fully EV trained...so that can be one reason why I'm having a hard time dealing the right amount of damage and countering beasts like Terrakion. Other than the obvious "get stronger IV'd Pokemon", what else can I do? Not too many people willing to give up a good Pokemon like that for almost nothing in return (see my trade thread--meaning I don't have much to offer). But back on topic, this isn't a trade thread. Simply put, the last 3 that I have aren't where they should be.

Who should I replace, if at all to help counter something like Terrakion or Thunderus?

Why are you posting this on IN-GAME TEAM HELP? Go to where they discuss competitive battle, not in-game teams, sirreh.

I would say get one or two really good walls and burn him to cut his attack. Maybe a dusknoir or someone with wil-o-wisp.

Terrakion is far from uber.

Regardless it loses to bulk psychics like Mew, Slowbro and Celebi. Gliscor also does well against it. Priority from the likes of Scizor, Lucario (Vacuum Wave), Conkeldurr and Azumarril puts it quickly in its place.

Me in my threat list thread said:

Countering Terrakion] is quite difficult due to the phenomenal coverage of fighting and rock. Golurk and Claydol make good counters and resist both its STABS. Bulky psychics like Slowbro, Celebi and Cresselia work very well. Nidoqueen is a fantastic counter. If it hasnt Rock Polished things like ScarfChomp work. Priority is Terrakions downfall though, Scizors Bullet Punch, Lucario's Vacuum Wave, Aqua Jet etc all hit it for Super Effective. Bulkier walls like Hippowdon can KO as long as the Air Balloon is popped. Gliscor can work to an extent too, though boosted Stone Edges really hurt it and Air Balloon hampers it too.

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