Personally, I find triple battles easier at PWT, mainly just so I get 6 Pokemon. So I would suggest you try and figure out which battle style is best for you.
Additionally, I'm not too sure what EVs you've given your Pokemon. I don't have their abilities/ natures either, so add that to your question, or I'll just assume...
Emboar @ Fighting/ Fire Gem
EVs: 252 Atk. 4 Sp. Atk, 252 HP
Flame Thrower/ Heat Wave
Depending on what battle style you choose, Heat Wave will be better in doubles or triples. I would not recommend Heat Crash, since it's based on your opponent's weight.
PWT is very offensive based, so I would recommend using a gem and OHKOing an opponent's Pokemon. Emboar isn't that great a fighting type anyway, especially when you have options like Scrafty and Mienshao.
Ampharos @ Electric Gem
EVs: 252 Sp. Atk, 200 HP, 56 Speed
You know, since you listed 4 Pokemon, I can only assume that you were battling in doubles mode. While you have 2 Ground types on your team, meaning Discharge won't affect them... but what if they both faint and you have Ampharos and Emboar out at the same time? Discharge = wasted move slot. You also already have Thunderbolt, why do you need a lesser powered version of it? (even though it does hit multiple targets)
Garchomp @ Dragon Gem
Ability: Sand Veil
EVs: 252 Atk, 252 Speed, 4 HP
Fire Fang/ Outrage
Why is Garchomp holding Amulet Coin...? It won't do anything at the PWT.
While Dig seems attractive because of its immunity turn, it's not a good move. Earthquake will do twice the damage in that turn, and while your opponent in the PWT won't usually change Pokemon, the rest of your team members can end up being KO'd, when Garchomp could have done something to prevent that, instead of digging a tunnel.
Also, Dragon Rush is a rubbish move in light of Outrage and Dragon Claw's higher accuracy.
Rhyperior @ Quick Claw (or whatever)
EVs: 252 HP, 252 Sp. Def, 4 Atk
Ability: Solid Rock
Horn Drill is a horrible move. It's an OHKO move that has an accuracy of: (level of user-level of target) + 30)%, aka 30% in PWT.
The chances of it hitting are so low that it's not worth bothering with, and even if you were at a high enough level for it to be useful, you'd be so overpowered that you can just use any move.
You have 3 Pokemon weak to Ground, 2 weak to Ice, 2 weak to Water, with nothing to wall any of those moves. All of your team are incredibly slow with the exception of Garchomp, meaning they will need to take a hit before being able to do anything. Additionally, as I mentioned, PWT is hyper offensive, meaning a lot of moves will be boosted by gems.
You also most likely have to face someone with Ground, Ice, Water and Grass moves, with Misty, Brock, Giovanni and Erika being around. I really suggest replacing some of your team members for faster Pokemon, and indeed Pokemon that resist some of the things your current team is weak to. I'm surprised you managed to beat the leaders of the other regions, considering the current spread of type weaknesses your team has.
A common strategy in doubles/ triples is to have a quick dual screener, like Espeon or Rotom, hold Light Clay, and set up Reflect & Light Screen ASAP.