A very risky strategy, if you mess it up, you've pretty much lost the battle, but if you succeed, you destroy your opponent. Here are a few of my thoughts as to how I would counter this team, exposing some flaws you would need to be ready for.
1.The minute you see a pokemon like ninjask or Mawile in the competitive scene, you know baton pass is coming, you said it yourself, it's all they're good for. So I could just use the move taunt and force them to hit me with weak attacks before they can get in any boosts.
2.Most of the time, ninjask will stall with protect to boost its speed. So if I don't use taunt, I would boost my own stats, predicting a switch based off of your team.
3.Huge fire weakness. Even with Swampert, the rest of your team has to be ready for fire type moves. both the pokemon you have to carry out your plan will fall to just about any fire move. On top of that, many non fire types come armed with flamethrower, so it requires careful prediction on your part.
4.Punishment would rip you apart, capped at 200 base power (300 on a dark type like houndoom, yikes!)
5.Mawile's defense might be pretty impressive, but it's the only worthwhile stat. There's not much point in setting up iron defense, seeing as nobody would hit it with a physical attack, most of the time, they'll abuse its low special defense.
6.You'll need a backup plan, since if this risky strategy fails, it could cost you the match.
On the plus side, this strategy has lots of potential... Perhaps have a team of powerful baton passers, and keep constant stat boosts throughout? Like have Umbreon for instance, with his low speed, you can safely switch in another pokemon so it won't get hit by the opponent.