I'm going to take a shot at this. Mightyena has terrible stats but if we're going to even attempt to use it, we may as look at what it had rather than just assuming it's terribad, and for my look I'm going to ignore Moxie, it's Dream World may boost it's attack by 1 stage per kill, but it's not worth it as it most likely is only hitting 1 at best.
Perhaps something like this would work for Mightyena.
Mightyena (F)
Intimidate
Jolly/Adamant
@Razor Fang/Life Orb
Astonish
Me First
Sucker Punch
Attract/Return/Rock Smash
The EV's I'm not sure of, and I'm disregarding the Elemental Fangs because Me First would probably be more usable as far as I can think. I just also wouldn't ever see a point to banding/scarfing Mightyena and it needs something that will give it a chance to not die to almost anything.
Whoa, what? Attract? Me first? Razor Fang? What are those accomplishing?
First off, attract. Why? Attract is very gimmicky and situational. You don't know what the other pokemon's gender will be. Even if attract hits, the opponent can easily switch out. They can then bring in a fighting type such as Sawk, which outspeeds mightyena, resists its STAB and will OHKO it with CC. You're giving the opponent a chance to switch out.
Me first- same thing with attract, except worse. If your opponent is, say, trying to set up a sweep, your doing nothing by copying their boosts. I can't even explain how bad me first is. In order for it to be effective AT ALL, you'll need to identify the set your opponent's Pokemon is running, and predict their next move, and decide if the move is effective against your opponent. If the opponent's Pokemon is offensive (chances are it will be in this meta and the Pokemon youre using), they'll likely use a STAB attack, which won't be dark type because they'll avoid resistance.
Most types resist themselves, so you'll hit the opponent with a resisted attack, and they'll hit you with STAB. Not a good trade.
I really can't criticize anymore because your intentions with this set are unclear, but assuming it's offensive, this is a very unstable set. It's very situational. Moxie is mighty's only positive aspect, and you throw that away?
Razor fang- 10 percent flinch rate? How is that helpful? Are you trying to finch your opponent to death with astonish and razor fang? Astonish would do so little damage! Leave flinching to dunsparce, seriously.
This set needs.... I don't know what...
