Singles Changes
Change Ice Fang on Gyarados to Bounce. Life Orb and Hail damage can really add up, especially when un-dynamaxed. Bounce/Max Airstream is STAB and boosts speed. If you can, get a Gyarados for Moxie (for singles, at least :P) and even less necessary, a Jolly Nature on Gyarados.
This may be a dumb idea, but I think running 252 Speed EVs on Conkeldurr and changing to Jolly would work, as well as with a moveset of Facade, Mach Punch, Drain Punch (or Close Combat for that extra punch), and Knock Off to hit ghost types.
I think you should change Ice Punch on Tyranitar to Fire Punch. Other than that, it's good.
Rotom-Wash's should serve as a more defensive Pokemon, in my opinion. I have too much to explain so I'll just give a moveset paste here of the changes I think you should make.
Rotom-Wash @ Leftovers
Ability: Levitate
EVs: 252 HP / 252 Def / 4 SpD
Bold Nature
IVs: 0 Atk (not necessary at all lol, made this on showdown so it's optimal)
- Will-O-Wisp
- Pain Split
- Hydro Pump
- Thunderbolt
Duraludon should be changed out, considering you already have a dragon type, and it's not as good in singles.
I'd suggest... a grass type? Really, you can slap on any fully evolved grass type Pokemon and it works. I was going to suggest a fire type too, but you'll see why I didn't below (in addition to having Fire Punch on TTar :P).
Dragapult should not have Leftovers if it's not defensive. Swap Leftovers for Life Orb, change from Jolly to Hasty Nature, and use a moveset of Phantom Force, Dragon Darts, Flamethrower, and Dragon Dance. Flamethrower will deal with the few steel types that can wall Dragapult.
Doubles Changes
Keep Intimidate on Gyarados. Change Ice Fang to Bounce for Max Airstream. Change Crunch/Earthquake to Power Whip for Gastrodons/Seismitoads, etc.
Put Assault Vest on Conkeldurr, change the defense EVs to HP EVs, and swap Guts to Iron Fist. Moveset will be Mach Punch, Drain Punch, Thunder Punch, and Rock Slide.
Put Weakness Policy on Tyranitar, change Ice Punch to Superpower (for Max Knuckle), change Stone Edge to Rock Slide, and change Earthquake to Protect. Also change Max Speed EVs to Max HP EVs and change to Adamant Nature.
Replace Rotom-Wash with Excadrill to form some synergy with Tyranitar. Make sure Excadrill is Sand Rush, and it can have either an Adamant or Jolly Nature. Moveset is High Horsepower (to prevent hitting allies), Iron Head, Rock Slide, and Protect.
Definitely change to Stalwart on Duraludon. Maybe change from Modest to Timid Nature too? Whatever works for you.
Again, change Leftovers to Life Orb on Dragapult. I'm not that good at VGC Dragapult sets, so keep that in mind. I think the moveset should be Phantom Force, Dragon Darts, Protect, and... literally anything else. Fly for Max Airstream? Steel Wing for coverage and Max Steelspike? Mostly anything works.
Hope this helped!
