Give Samurott Waterfall when you receive the HM, and Ice Beam when you get the TM; replace Aqua Tail and Water Pulse.
Suggested item: Leftovers
If you have enough shards, teach Scarfty Drain Punch via move tutor at Humilau (10 yellow shards) and Ice Punch at Driftveil (10 red shards). Replace Chip Away and either Brick Break or Hi-Jump Kick. I suggest you replace Hi-Jump Kick, because Scrafty is slow, so it's bound to take a hit or two before it can do anything, and it could potentially KO itself when missing with HJK.
Suggested item: Expert Belt
Excadrill looks good; I would go for Iron Head instead of Dig, since you already have E-quake, but that's just me. Later on, you'll need Strength, so you might want to give your Excadrill that.
Suggested item: Soft Sand/ Expert Belt
Give Chandelure Shadow Ball (by TM) instead of Shadow Claw. It's sp. Atk is massive, so make good use of that. Also replace Flame Burst with Flamethrower when you get the TM, and Psychic instead of Hex.
Suggested item: Shadow Tag
Your movesets aren't horrible, they just need a little shuffling. This is also in-game, meaning if you're high enough of a level, anything moveset/ Pokemon combination will work.
So the main thing right now is your Ground weakness; Excadrill and Chandelure. You also need a Flying type for HM Fly. You also have 2 Fighting weaknesses with Excarill and Scrafty, and while Chandelure is there to take Fighting hits, it'd be nice to have a back up in case Chandelure faints.
Ability: Big Pecks
Item: Rocky Helmet (or whatever else is available to you)
- Punishment/ Foul Play
- Aerial Ace/ Brave Bird
- Toxic/ Roost
Mandibuzz has good bulk, a nice typing that makes it immune to 2 things, neutral to Bug and Fighting, and 3 resistances.
Mandibuzz is available every Thursday on Route 4 in your game, but always has Weak Armour. Vullaby can be found on Route 23. If you need something with Fly desperately, I suggest get a Ducklett from Driftveil and use that until you get a Mandibuzz/ Vullaby.
Thinking about it now, you haven't really got something that's super effective against water. Even if you TM'd Chandelure Energy Ball, it's still weak to water types, meaning it'll take a dent in a battle.
Ability: Compound Eyes
Item: Wide Lens
- Bug Buzz
- Volt Switch
- Energy Ball/ Giga Drain (Giga Drain is move tutor move)
The unique Bug/Electric typing means it only has 2 weaknesses (Rock and Fire) and 4 resistances. Compoundeyes will boost its accuracy by 30%, meaning Thunder's accuracy is now 91% instead of 70%, allowing Galvantula to use that move without Rain. Give Wide Lens if you want Thunder to be 100%.
You can catch a Joltik with Compoundeyes in Chargestone cave (it's pretty easy, since the other ability it could have is Unnerve, and that always triggers a message just as you encounter the Joltik. If there's no message, it's ability is Compoundeyes).
However, Galvantula will be adding another Rock weakness to your team, and if you choose Mandibuzz, half your team will have a Rock weakness. I just thought Excadrill and Scrafty can take Rock hits, so that's why I suggested Galvantula.
B2W2 TM list
B2W2 Move Tutors
EDIT EDIT EDIT
Ability: Inner Focus
- Haze/ Roost
NB: no item because Acrobatic's power doubles when the Pokemon is not holding an item. Fly isn't a good battle move
Item: Miracle Seed
- Giga Drain
- Sleep Powder
- Brick Break
- Wring Out
Wring Out is a pretty useful move at the beginning of the battle (since its power is higher if your opponent's HP is higher).