Okay if there was certain strategy to beat Mann vs Machine what classes and what weapons would be required to beat a match of say... A seven wave round on a server that can allow eleven players?

For me I think my strategy were to have two engineers with sentries. A Pyro with a Rainbower, a flare gun, and a volcano shard axe. Two soldiers, one with a Cowmangler 5000, Buff Banner, and that whip; the other with a Direct Hit, an enforcer, and a Equalizer. Two Medics, one with a regular Medi-gun, Cursaders Crossbow; the other with Kritzkrieg, an Overdose and both would ubersaws. Two Heavies, one with the Brass Beast, Sandvitch; the other with a that dragon mini gun, and it doesn't matter what melee weapon it is. A Scout with a Force-O-Nature, Krit-a-cola, and a Fan of War. And finally a Demoman with a Grenade Launcher, a Sticky launcher, and an Eyelander.

So what are your's

If you've got eleven players, you don't need strategy. (Except maybe on wave 666? That would probably still be a challenge.) Pick the silliest guns you want and go hog wild. Try some fun upgraded weapons. Zatoichi Demoknights, Righteous Bison brigade, Spies with especially pointy hats - whatever you feel like throwing upgrade money at.

Yeah with that many people, unless there's some buffs on those robots, all those robots are just a scrap heap. I've only done MvM with more than 6 players a couple of times.

Now, for 6 player MvM, I've got some nice strategies. The meta, which works well usually, is Scout, Soldier, Demo, Heavy, Engie, Medic. That gets old after a while though. More fun strategies can replace the scout with spy, demo or soldier for sniper, heavy for pyro. You're almost always going to need the medic for the projectile shield, the engie for ammo, someone to get money, someone to take out medics, someone to give you near-constant mini-crits, and someone to deal lots of damage.

I think my favorite time was when some friends and I beat Bavarian Botbash (on Mann Up) with 3 pyros and combat medic. Ahh... good times.

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Wave 666 pretty much has only one strategy. Only one that I've heard of working anyway.

4 or 5 soldiers, a combat medic, and maybe an engie. That spy and tank wave man... 0.0

Dunno. I'd probably just cover the basics. Brass Beast Heavy, Kritz Medic, Engineer, Scout with Mad Milk, Spy, Sniper with Jarate... Everything else is pretty much just kinda... whatever. You've got all the CC, damage and sustain you'd need.

When I play with my friends I play Pyro and have found the compression blast indispensable. It's possible to use it to shove a bomb-carrying bot off the point even as they make the final jump. I guess anything with knockback would do, e.g. Force-A-Nature.

I've also noticed how dearly critical it is to upgrade your defenses. Know the order of your foes and build resistances accordingly. Blast resistance is godsend, and with how many all-crit enemies there are and how cheap crit resistance is, it's silly not to get it.

Also, when there are a lot of tanks (666), we've found a very efficient method is a Pyro with maxed-out flamethrower damage (not burn time, not burn damage, just raw damage) and a Kritz medic on him. (It's recommended to have plenty of ammo for this, though.)

And a few more things. Medic's shield is good. Heavy with destroy projectiles is good. Heavy at dispenser is good.