Your team is really tanky, which I guess is alright, but I notice that you're really heavy on the SDef side and not so much with Def.
Here's what you need to do. Changes will be in bold or caps.
Reuniclus @ Leftovers
Ability: Magic Guard
EVs: 252 HP / 252 SAtk / 4 SDef
QUIET Nature
IVs: 0 Spe
- Trick Room
- Psychic
- Focus Blast
- Shadow Ball
Reuniclus definitely has potential as a SDef tank, but in the context of your team, he's better as a sweeper. Have you seen Reuniclus's base SAtk? Well, it's a whopping 125! And its Spd is a horrific 30, but that works great for you on a Trick Room team! So let's put that massive TR sweeping potential to use with some heavy investment in SAtk. Keep your HP EVs instead of putting them into SDef, since they'll help cushion any physical Dark- or Bug-type attacks. Also, switch to a Quiet nature to maximize your SAtk. Your movepool is good, except you don't need to waste a slot on Recover since you have Wish on Sylveon. Instead, run Shadow Ball to nail Ghosts with.
Malamar looks good as a physical sweeper. So OP on a Trick Room team.
Sylveon @ Leftovers
Ability: Pixilate
EVs: 252 HP / 252 SpA / 4 SpD
QUIET Nature
- Yawn
- Hyper Voice
- Protect
- Wish
Hyper Voice is more powerful than Moonblast when coupled with Sylveon's Pixilate ability. Go Quiet again here-- it'll help slow you down instead of just subtracting from a useless slot. I suggest Yawn over Psyshock because you don't really need it, since Fairies eat Fighting-types anyway. Yawn will be effective in forcing out opponents trying to set up on you.
As far as Ampharos goes, Rotom would be a much more practical choice. Use Rotom-H to help with your Bug problem. You don't have a troll Pokemon yet, so let's run a Specs set, just for giggles.
Rotom-H @ Choice Specs
Ability: Levitate
EVs: 252 HP / 252 SAtk / 4 SDef
QUIET Nature
IVs: 0 Spd
- Volt Switch
- Trick
- Will-O-Wisp
- Thunderbolt
Rotom would make a feasible lead, with its potential to upset a hazarder via Trick or switch out with Volt Switch. After crippling a hazarder, you could predict the opponent's frustrated switch and utilize the turn to Volt Switch to a Trick Roomer. It's also got the potential to quickly destroy a physical sweeper with Will-O-Wisp. Tricky, eh?
Dusclops looks fine-- just switch the EVs in SDef to Def, because you don't have a physical tank yet.
Now you need another slot. A physical attacker, for one thing. I know just the thing.
Conkeldurr @ Life Orb
Ability: Iron Fist
EVs: 252 HP / 252 Atk / 4 SDef
Brave Nature
- Drain Punch
- Ice Punch
- Knock Off
- Hammer Arm
This is Conk, your new big, fat, slow powerhouse. Iron Fist will boost the power of Drain Punch and Ice Punch. Drain Punch restores your HP while you wreck. Ice Punch will nail some types that you didn't have coverage for yet, while Knock Off covers Psyhic-types and offers serious crippling capabilities. The best part is the ridiculously powerful Hammer Arm, which has an effect of lowering your Speed-- to your advantage here. Kudos to Lusty for reminding me that I was using the wrong Conk set for TR.
I hope this helps you.