You should also consider Honchkrow; you don't have any flying-types on your team, and that would make up for it.
Mandibuzz is part flying too, so she's got that lane covered there :)
So I'm doing a dark monotype run on Y and have been trying to plan out my team. I think I want it to look like this:
Greninja
Cacturne
Weavile
Mandibuzz
Absol
Drapion
I've been considering replacing Greninja with Crawdaunt since I've never used one. I'm pretty dead set on all the other ones except Drapion. What do you guys think?
Hey! Trust me, if this was Gen 5 I would probably just recommend you go with a team of 5 Scrafty + a flier but that wouldn't work out so well in Gen 6 now :'( You have a ton of options open to you, but most of them should revolve around making sure that battling fairies and bugs are as trouble free for you as possible. With all this, I would recommend either
Houndoom or Bisharp: Houndoom gives you a cool fire/water/grass core between Greninja and Cacturne so you have more type coverage on your team, is neutral to fairy, gives you another option for a MEvo and greatly helps you vs Wilkstrom. He also looks like a don ;) Bisharp is just your full stop to fairies and does the job better than Drapion would with STAB Iron Head while rampaging through the gym leaders, 2/4 E4 and Diantha by himself. If you're willing to breed for one, then Crawdaunt's a better option than Greninja as it's much stronger and can fix its speed issues with Aqua Jet. The inner trumpeter in me says you should go for Crawdaunt anyway and bask in the glory of half your team coming from Hoenn just in time for the remakes haha.
Um movesets ok
Greninja - Dark Pulse, Surf, Ice Beam, Extrasensory (Fighting mon suck)
Crawdaunt (make sure its ability is adaptability!) - Surf,/Waterfall, Crunch/Dark Pulse, Dragon Dance/Swords Dance, Superpower/Rock Slide/X-scissor
Cacturne - Energy Ball, Dark Pulse, Focus Blast, move
Weavile - Ice Punch, Night Slash, Brick Break, Strength (something has to learn it for victory road *shrug*)
Mandibuzz - Fly, Nasty Plot, Air Slash, Dark Pulse
Absol - Night Slash, Psycho Cut, Megahorn, Play Rough
Houndoom - Dark Pulse, Flamethrower, Sludge Bomb (anti-fairy), Thunder Fang (more water insurance)
Bisharp - Iron Head, Night Slash, Swords Dance/Power-up Punch, Sucker Punch/Poison Jab
These would be your 'best' movesets but they're not all that ingame friendly if I'm honest; Absol and especially Crawdaunt will be a pain to breed, Weavile needs Ice Punch or it will have no physical Ice STAB at all and Mandibuzz takes a while to get all its moves together. If you're willing to do a bit of preparation beforehand then that's alright, if not just shout and I'll try and put together a more accommodating moveset. To be honest it shouldn't matter anyway since Dark is a very spammable type :P
Good luck!