Individually, I think all your Pokemon are great. They have well balanced movesets, well though out EV's, and great abilities. But I think in the pursuit of this, I think you may have forgotten to diversify your typing. You have a Ghost and Dark type, (Cofagrigus and Houndoom respectively,) but both have very similar type advantages over Ghost and Psychic types. Plus, Heracross has a great Dark type move. Having two Bug types I would say is unnecessary.
So my suggestion would be to replace Yanmega and Cofagrigus with some maybe Flygon and Abomasnow, for all around better type coverage. And don't worry so much about maxing out only two stats, Pokemon are meant to be well rounded. I mean, I wouldn't really bother working on Heracross' SpAtk, but take into account his weak Def and maybe allocate some EV's into buffing that out.
Great job, and good luck in your endeavors!