Dragapult is generally a better Ghost type special sweeper, but if you want to keep Gengar switch Energy Ball to Sludge Wave and make it Timid instead of Modest.
Switch Tangela to Tangrowth. You can use a Rocky Helmet physically defensive set or a Assault Vest set. Try something like this:
Tangrowth @ Assault Vest
Ability: Regenerator
EVs: 252 HP / 4 Def / 252 SpD
Sassy Nature
- Giga Drain
- Knock Off
- Sludge Bomb
- Earthquake
Mandibuzz is not a good special set up sweeper, use it as a bulky pivot and defogger. If you want a Dark type Nasty Plot sweeper, I recommend Hydreigon.
Hydreigon @ Leftovers
Ability: Levitate
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Nasty Plot
- Dark Pulse
- Earth Power
- Roost
Mandibuzz @ Heavy-Duty Boots
Ability: Overcoat
EVs: 248 HP / 92 Def / 152 SpD / 16 Spe
Impish Nature
- Foul Play
- Roost
- Defog
- U-turn
For an offensive Scizor, give it Life Orb and replace Bug Bite with Knock Off because it doesn't really need Bug STAB, and replace Aerial Ace with either Sand Tomb or Psycho Cut to deal with Toxapex.
For Azelf, you're better off just switching it to Mew, who has much better bulk and a wider movepool.
Mew @ Heavy-Duty Boots
Ability: Synchronize
EVs: 248 HP / 148 SpD / 112 Spe
Jolly Nature
- Spikes
- Knock Off
- Taunt
- Roost
For Garchomp, switch Yache Berry to Life Orb for extra power and Iron Head to Fire Fang for Ferrothorn and Corviknight.
