No offense, but this looks like you took a bunch of Smogon Singles sets and slapped them on a VGC team, which is evident by your waste of EVs. This does not work, my friend. VGC and Smogon are completely different playing fields. I'll try to keep changes minimal, for now. All changes will be in bold.
This team looks good at a glance, but once we get into your spreads, movesets and items it begins to fall apart. It has a slight resemblance to the Japan Sand archetype, so I'll try to model it around that.
Your Old Team
Your New Team
Excadrill@ Focus Sash
Adamant | Sand Rush
4 HP / 252 Atk / 252 Spe
- Iron Head
- Earthquake
- Rock Slide
- Protect
Tentacruel doesn't really have a role to play in VGC, and you already have Rotom as your bulky Water. Your team is also pretty slow. So, I thought Excadrill would be a nice fit for a Sand team. Focus Sash makes up for his frailty. Iron Head OHKOs most Sylveon and offensive Gardevoir. Earthquake is a powerful spread move that deals with things like Aegislash and Mawile. Rock Slide is for those flinches and key KOs on things like Charizard. Protect is vital because of Exca's inability to tke hits and to punish double-targets.
Conkeldurr@ Assault Vest
Adamant | Guts
EVs: 212 HP / 84 Atk / 124 Def / 88 SpD
IVs: 15 Spe
- Drain Punch
- Mach Punch
- Ice Punch
- Knock Off
Conkeldurr is pretty good, but the way you're using it is wrong. I changed it to the bulky Assault Vest variant. Your team is also quite weak to status like Spore, Will-o-Wisp and Thunder Wave, so Guts lets you punish predicted status moves. Knock Off is used over Stone Edge for accuracy and the ability to rid the opponent of Sitrus Berries and Choice Scarves. I swiped the EV spread from Nugget Bridge. It survives Hydreiogn's Draco Meteor 100% of the time. The IVs let it underspeed minimum speed Aegislash, letting it KO it in Blade Form.
Rotom-Wash@ Sitrus Berry
Calm | Levitate
252 HP / 44 Def / 92 SpA / 100 SpD / 20 Spe
- Hydro Pump
- Thunderbolt
- Thunder Wave
- Protect
Rotom is very good on Sand teams. This EV spread and a Calm nature survives Solar Beam from Charizard most of the time, while also OHKOing bulky Landorus with Hydro Pump. Your team lacks speed control, so Thunder Wave is more useful than WoW and has good surprise value. Protect keeps Rotom in the fight longer.
Tyranitar@ Choice Scarf
Jolly | Sand Stream
252 Atk / 252 Spe / 4 SpD
- Rock Slide
- Crunch
- Ice Punch
- Low Kick
Tyranitar becomes the main attraction and setter of sand with Sand Stream. Choice Scarf and a Jolly nature lets him go fast and speeds up your relatively bulky team. Ice Punch handles most Landorus and Salamence after some chip damage. Low Kick KOs other Tyranitar, Terrakion, and Heatran.
Scizor@ Life Orb
Adamant | Technician
252 HP / 252 Atk / 4 SpD
- Bullet Punch
- Bug Bite
- Roost
- Protect
Scizor appreciates the Life Orb to help him pick up KOs on Sylveon and Gardevoir. On Sciz's EV spread, as with most of your other Pokémon, you were wasting EVs. At Lv. 50, the first 4 EVs equal one point, while every 8 EVs after that equal one stat point. This makes 248 EVs the same as 244 EVs, etc. For the sake of simplicity, Scizor gets a plain 252/252 spread. In VGC you rarely get time to set up Swords Dance without redirection, which you do not have. Therefore, Protect lets Scizor survive to dish out more pain.
Salamence@ Salamencite
Timid | Intimidate
68 HP / 4 Def / 244 SpA / 4 SpD / 188 Spe
- Hyper Voice
- Flamethrower
- Dragon Pulse
- Protect
Salamence is better than Gardevoir on Sand teams, but you could experiment with both. The EV spread outspeeds max speed Thundurus before it can OHKO you with HP Ice. Hyper Voice is potent Aerilate spread STAB that 2HKOs most of the metagame. Flamethrower handles Ferrothorn and Aegislash. Dragon Pulse is STAB to let you hendle other Dragons and hit Pokémon that resist Hyper Voice and Flamethrower.
This team had a lot of buried potential, and I hope I've helped you realize that. I hope my changes bring you some degree of success!
