We need to do something with yor Stoutland. If it has an ADAMANT nature so you must use physicall attacks.
Ev's: 252 Att. 124 Speed 124 Defense 6 HP
Trait: Sand Rush (Makes him speedy and scary)
Fire Fang (Coverage)
Wild Charge (Water and Ice moves will be a headache for you)
You should use Return (STAB and more dangerous than Hyper Voice)
Gastrodon is a good election because you will face a lot of water teams with stab moves
Ev's: 252 Defense 252 Sp. Def. 6 Hp
Trait: Storm Drain (When hit with a Water-type move your special attack is boosted.You don't need Sand Force because you are using it as a wall)
Ice Beam (Combined with Scald works well)
Recover (No comments)
Scald (STAB + It may burn)
Toxic (Help with walls)
Flygon is well but in my opinion you should change "Dragon Pulse" and add Dragon Claw. And possibly EV'S to Speed.
You must get rid of that Darmanitan, a better option is
Excadrill@Chople Berry/Life Orb/Air Ballon (you decide your necessity) UBER
Trait: Sand Rush
Sword Dance (An useful attack to be a monster)
X-Scissor (Coverage in GRASS types)
Earthquake (STAB and the most amazing attack)
Rock Slide (It works really great with Earthquake)
Rhyperior is great because it has a great Atk and Def. It's problem falls in it's poor Special Defense and Speed. Remember the Sand Storm boosts the special defense of Rock Type Pokémon (50%).
Ev's: 252 Attack. 48 Speed. Defense 208 HP
Trait: Solid Rock (Reduces damage from super effective hits by 1/4. That's perfect to it's Special Defense in Sand Storm )
Earthquake (Combo with Rock Blast/Stone Edge)
Rock Blast or Stone Edge ( Rock Blast to break Substitutes or Stone Edge if wou want)
Dragon Tail/Roar (Phaze and help the Stealth Rocks)
Lucario is a decent sweeper in Sand Storm by special side. It is inmune to toxic, sandstorm and give you stab moves differents.
Lucario@Life Orb/Focus Sash
Ev's : 252 Special Attack, 252 Speed, 4 HP
Hidden Power Ice or Psychic