Banette: It takes 4 EVs to boost a stat by 1 point, and Pokemon almost always rounds down. You just wasted 4 of your EVs there. Since mega Banette won't outspeed many foes at base 75 speed, you should just max out physical attack and give it an adamant nature. 2-turn moves are generally not viable in competitive, as they offer a free turn to switch or set up. Replace Phantom force with shadow sneak or shadow claw. I have no idea what you're doing with gunk shot, so replace that with destiny bond. It's a status move, so mega Banette's ability prankster makes it go first regardless of the foe's speed.
Exploud: Adamant will decrease your crucial special attack and increase your useless physical attack, so replace it with modest, which will do the opposite. Replace soundproof with scrappy because there aren't many Pokemon with sound moves in competitive. Since that way boomburst hits ghost types for neutral damage, replace shadow ball with surf for more power.
Pikachu: With a base stat total of 320, it's less than all fully evolved Pokemon except Shedinja, Smeargle, and Ditto, and even less than many Pokemon that aren't fully evolved. This Jolteon set will play a similar role, albeit better.
Jolteon @ choice specs/life orb
Ability: volt absorb
EVs: 4 HP/252 SpA/252 Spe
Timid nature
-Thunderbolt
-Volt switch
-Signal beam
-Hidden power grass or ice
This can be used as a sweeper. Signal beam is used on grass types that resist electric attacks, the hidden powers are used on ground types. Which hidden power you use depends on which ground types you see more often. Volt switch is used in case you use a choice item and anticipate a switch into a Pokemon that resists electric, so you get to switch out and not be choice locked into an electric attack.
Vespiquen: If you really want this to be a mixed wall, give it 180 physical defense EVs and 76 special defense EVs. Its defenses are almost balanced this way.
Tyrantrum: Since most fairy attacks will probably OHKO this, apicot berry isn't very useful. Give it a life orb. If you really want to kill fairies, replace earthquake with iron head. For fast sweepers, speed is usually more important than attack, so replace adamant with jolly.
Braviary: Brave nature decreases speed, which is crucial to Braviary. Replace brave with jolly, so it decreases the useless special attack stat and increases speed. Again, 2-turn moves are generally not viable, especially here, where a foe can easily OHKO Braviary while it's using sky attack. Replace that with brave bird. Replace hone claws with return (because you probably will have no time to set up) and zen headbutt with superpower (for ice, rock, and steel coverage). Since none of its moves now take advantage of sheer force, replace sheer force with defiant.
