Barraskewda: Leftovers is useless on Barraskewda. It would be knocked out easily. Try Life Orb or Choice Band. The rest of the set is good, but try Close Combat over Ice Fang or Aqua Jet.
Cinderace: Perfect Set.
Skarmory: There is a flaw in the set here. It is crippled by a special attacker. EV Spread needs to be improvised. Believe me, guessed EV spread in PS! isn't always good. You don't need speed at all. You already have Lando as a Defogger, so why Defog on Skarm? Replace it with Roost. Actually speaking, it is outclassed by Ferrothorn. However, I would give you sets of both.
Skarmory @ Leftovers
Ability: Sturdy
EVs: 252 HP / 4 Def / 252 SpD
Calm Nature
IVs: 0 Atk
- Roost
- Spikes
- Stealth Rock
- Toxic
Ferrothorn @ Rocky Helmet
Ability: Iron Barbs
EVs: 248 HP / 252 Def / 8 SpD
Impish Nature
IVs: 0 Atk
- Leech Seed
- Stealth Rock
- Toxic
- Body Press / Power Whip
Dragapult: All the set are good except one. Dragon Tail is useless here since it is too frail, so you can replace it with Sucker Punch. I think that Infiltrator is better than Clear Body, but it is up to you.
Dragapult @ Life Orb
Ability: Clear Body
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature
- Dragon Dance
- Dragon Darts
- U-turn
- Sucker Punch
Landorus-Therian: Good set
Hydreigon: The set you are using is good.
Improved Version: https://pokepast.es/8ab4717ae818f332
Hope this helps :)