Your team is decent. However, I see three problems:
- Luxray is outclassed by Electabuzz and Eelektross.
- You have two Rock Weakness and zero resist.
- Meganium's job is also done by a quicker Pokémon, Serperior.
So here are my changes:
- Haunter > Drifblim
- Roselia > Meganium
- Eelektross > Luxray (Unless you really wanna keep an outclassed, yet your favorite Pokémon)
- Mandibuzz > Armaldo
So welcome to your new team:
Yes, the team is half Unova.
Samurott
Prefer the mixed Samurott, as it will not be walled easily. If your opponent see you using Swords Dance, they will run Seismitoad. Mixed Samurott can block Toad with Grass Knot.
@ Salac Berry:
Trait: Shell Armor / Torrent
EVs: 196 HP / 52 Atk / 200 Sp.Atk / 56 Speed
Hasty Nature
- Substitute
- Hydro Pump
- Ice Beam / Megahorn
- Grass Knot / Aqua Jet
It is up to you, first, to keep your Samurott, but I wouldn't. I prefer SubSalac because on its own, Sub does what Lum Berry does: Block Ailment, but Sub is better because it does it permanently in exchange of HP, and when you get down to 25 %, Salac Torrent Time! You simultaneously get a Water Boost, launching powerful STAB Hydro Pump, sitting at a good Speed, now, because of the +1. Before, you were at a 248. Now, you are at a 320 and +. Now, the tough choice is between Torrent or Shell Armor, because the former offers a stronger Hydro Pump while the latter secures you of critical hits, letting you setup Substitute comfortably. I would opt for Torrent. Between Megahorn and Ice Beam, it is up to you if you want to attack Jynx, Musharna, Tangela and more with Megahorn or prefer the Special Samurott and reconsider the EVs: 252 Speed / 252 Sp.Atk / 4 HP. I would opt again for the well coveted Megahorn because of Jynx and Musharna which are common per team.
Haunter
Haunter has some niche in the tier: It is the quickest Ghost, it is successful for a NFE, boasting a usable 115 Special Attack, and 95 Base Speed is nothing to laugh at. It also carries a good typing, destroying Toxic Spikes on its way as well as a good combination of STAB.
@ Black Sludge:
Trait: Levitate
EVs: 252 Sp.Atk / 252 Speed / 4 Sp.Def
Timid Nature
- Substitute
- Sludge Bomb
- Disable
- Shadow Ball
Like its father, Gengar, Haunter can use a SubDisable strategy to restrict your opponent using their best move for a certain period of time. Black Sludge recovers your HP more than Lefties does, and if some trickster come on, you know what to do: Let them take the Black Sludge, as if you receive a Choice Item, you become a sweeper with Haunter.
Roselia
This one's job is, like Puppy Roserade, set up Spikes, Toxic Spikes and asleep foes with the now legal Sleep Powder + Toxic Spikes + Spikes, except if you play Gen5. If you do, then just say it in the comment. Roselia gets a decent bulk with Eviolite, so you won't be fainting quickly.
@ Eviolite:
Trait: Natural Cure
EVs: 252 Speed / 252 Sp.Def / 4 Sp.Atk
Timid Nature
- Spikes
- Toxic Spikes
- Sleep Powder
- Giga Drain / Sludge Bomb
It's up to you for the last attack if you want recovery or power. I would chose Giga Drain.
Camerupt
EVs: 252 HP / 252 Sp.Def / 4 Sp.Atk
Fine.
Mandibuzz
Physically Defensive Buzz:
@ Leftovers:
Trait: Overcoat
EVs: 112 Speed / 248 Def / 148 HP
Bold Nature
- Foul Play
- Toxic
- Defog
- Roost
You gotta play fastly defensive. With Defog and Overcoat, you have a key: Block Powders and Hazards as well as Leech Seed, which is vital for your team's resistance. Foul Play will make usage of foolish high attacks your opponent wanna boast against you, and Toxic is for Stallbuzz.
Um, Electric
Um, Luxray :/
Luxray is outclassed by Electabuzz and Eelektross, the latter which see usage even in UU. Luxray has a solid attack, but it lacks Speed. Eelektross is slower, but it has a colorful movepool in Aqua Tail, Coil, Crunch, Flamethrower, Thunderbolt, Volt Switch, U-Turn and many more, and Electric Pokémons would kill for this movepool.
Use Eelektross, unless you really love Luxray as much as I love Arcanine.
@ Choice Band:
Trait: Levitate
EVs: 252 Atk / 252 HP / 4 Def
Adamant Nature
- U-Turn
- Wild Charge
- Aqua Tail
- Drain Punch
Fills the same role as Luxray, but has better movepool and no weaknesses, thanks to Levitate.
Or use Luxray:
@ Choice Scarf:
Trait: Intimidate / Guts
EVs: 252 Atk / 252 Speed/ 4 Sp.def
Jolly Nature
- Wild Charge
- Ice Fang
- Superpower
- Volt Switch
Guts or Intimidate is tough, because the former allows Luxray to be a nice Ailment Sweeper, while the latter cuts attack from threats such as Regirock, which is 2HKOed by Superpower.
Wild Charge is your premier STAB, and Ice Fang give coverage against Ground. Slow Volt Switch is good to have.
Hope this helps!
~ Sincerely yours, Blitz of Justice.