So what classes should be played? Its simple really. Scout, Soldier, Pyro, Heavy, Medic and Engineer. This setup provides the most diverse, best damage potential and overall utility needed to defeat any wave that's thrown at it.
The Scout
Primary: ScattergunSecondary: Mad Milk
Melee: Sandman
MvM Job: Money Grabbing, medic/sniper picks
Upgrade Priority: Resistances, Milk Speed, Sandman Mark on Hit
The Scout is essential to a successful Mann up engagement. Money is the life blood of the merc's ability to obliterate later stages of any map, and the Scout is the number 1 class for picking up money. As a scout, your primary job is to get that money. Any lost money is a direct reflection on your ability, and those $100 bonuses add up. When you aren't grabbing money your focus should be on taking out snipers and medics. A full scattergun shot on a medic will one shot it, this is important when the Soldier is out of range or out of Crit canteens.
Depending on the map, the -35% speed upgrade on your Mad Milk is one of the most critical upgrades in the game. It slows down giant scouts, and keeps your team healed up with it's natural ability. Its wide spread is also great for slowing down large groups of small scouts. The next upgrade on your list should be the Sandman's Mark target on hit, $500. It allows you to mark a target from a distance and let your team kill it much quicker. It is vitally important to both Milk and Mark a giant bot from a far since you'll be torn to shreds if you get too close. For this reason alone, the Sandman is much better than the Fan of War.
While it completely depends on the map, your upgrade stratgey should be resistances first. Because money is so important, you don't want to die and want to be able to survive encounters in the midst of a bot horde. I typically get Blast/Bullet to max, Fire resistance and on the waves that matter at LEAST 2 points into critical resistance, without it Giant soldiers will ruin your day. Getting at least 2 levels in Mad Milk recharge rate is essential for later waves, it should be spammed at any large group of bots, and always be ready for giant scouts.
Upgrading your scattergun is unneeded as it does plenty of damage on its own. Its great for taking out all the small bots (sans Fists of Steel heavies) and can One-shot a good chunk of them with a solid body shot. Your main job isn't to kill, so focus on Resistances/Milk/Sandman Upgrades.
Don't forget about the money, ever.
The Soldier
Primary: Beggar's BazookaSecondary: Buff Banner
Melee: Escape Plan
MvM Job: Indiscriminate carpet bombing
Upgrade Priority: Rocket Reload, Rocket Clip Size, Rocket Ammo Capacity, Rocket Damage
As a soldier, your primary job is to carpet bomb the hordes of robots coming in. Try not to stand too far to avoid the "50 damage syndrome" and move up close to get some extra damage bonus. Once upgraded you are a true force to be reckoned with.
While the stock rocket launcher is an excellent weapon for Mann vs Machine, the Beggar's Bazooka is just a better overall choice. Between doing more damage during crit canteens, to a better spread for uber medic slaughtering, the Bazooka is significantly better than the stock. Both can be used with equal effect, but the Bazooka is just better since it works with Kritz Medics and crit canteens more smoothly.
You are a roaming glass cannon. Stay close to the front lines for as much damage as possible, but don't get too close. Since rocket launcher upgrades are so expensive, you can't feasibly fit in enough resistances to make a difference.
Make sure to communicate with your medic to get the most out of his krits during tank rounds. Have him krit you for your volley of 9-11 rockets, then quickly switch over to the heavy. Don't let him waste valuable krit time while you reload.
Upgrading is pretty fluid for the Soldier. The first upgrades you should get is the reload speed. Less time you spend reloading, the more damage you do. After that, Firing speed, Clip size, total ammo, and if really needed +hp on kills. Rockets do plenty of damage on their own, so throwing 400 for a 20% damage bonus can wait for later waves when you're done with the needed upgrades.
The Medic
Primary: Crusader's CrossbowSecondary: Kritzkrieg
Melee: The Amputator
Hat: Team Captain
MvM Job: Healing, Kritzing, Pyro buddy
Upgrade Priority: Uber charge rate, Uber Charge duration, Heal Speed, Over-heal amount, Vial sharing
You are the life blood of the team. Without you, your team will constantly die and have to respawn. With you, your Pyro will be useful in horde waves, and your heavy able to stand toe to toe with a Deflector Heavy. You are also the eyes and ears of your team, calling out spies, spotting snipers and calling out cash locations for the scout.
During the early waves, you should be up close and personal with the pyro. Keeping him alive should be your utmost priority. Once the game progresses and he has his resistances up, you can move back to the heavy for the larger robots.
Kritizing is the most important thing you can do. Either the pyro or heavy are the best bets, early I suggest going with the pyro, then later on moving to the heavy. Once you get vial sharing, load up on crit canteens and spam them during recharge times. Since you are a non-damage class, adding crit canteens and kritz will make up for your loss, even (if played perfectly) add more damage than another damage dealing class would.
Keep your eyes open for dangers, and play defensibly and keep your team aware of spies and possible snipers. If you have to go chase down a bot, something has gone seriously wrong.
The Pyro
Primary: Stock Flamethrower
Secondary: Flaregun/Shotgun
Melee: Homewrecker
MvM Job: Airblasting, health reducer
Upgrade Priority: Resistances, Flamethrower ammo, Flamethrower Airblast Power
Mmmph Mmmph Mpph. Mmmph Mmmph mmmmmph mph! mmmmph mmmmmm, mmmmph mph. mmmmph mph mmph. Hurrrrrrrrruuuuuu!
Your job is simple. Keep the bomb from reaching its target. Know your bomb reset locations and airblast those bots back to hell. Outside of playing pong with the bots, your job is to do as much damage as possible. During horde waves, get up close with the medic and go wild. During tank waves, let the tank push you while ducking for extra damage to bots behind the tank. Keep your eyes on the sides and be ready to airblast bomb carriers or giant robots that try to get past it.
Load up on uber canteens, it will make airblasting giants on the decoy missions MUCH easier. Try to upgrade equally however, getting extra ammo, airblast power and resistances all at the same time. Health on kill is nice but not necessary beyond the first wave or two and frankly kind of a waste, same goes for afterburn damage and time.
Make sure you know where the bomb is at all times, and have your team work with you to keep a "toy" robot with the bomb in a constant circle. If you can keep it up, they'll never be able to cap the bomb.
Outside of the primary Flamethrower upgrades and resistances, don't bother upgrading much else. Save the money for uber canteens. On later stages it will take 1 uber to push 1 giant robot to the reset area. Keep this in mind when you think about getting Jump height, or homewrecker damage or any other useless upgrade.
During tank rounds, get up there with the heavy, duck and let the tank push you while you shoot it. Your flames will go through it and hit the robots behind it doubling your damage. When it gets to the "line" (aka, where the heavy normally sits) back off and go after the bots that spawn, and bring the medic with you.
You make the difference between winning and losing on some of the harder missions more than any other class.
The Heavy
Primary: Stock MinigunSecondary: Sandvitch
Melee: Gloves of running urgently
MvM Job: Damage, Crowd Control
Upgrade Priority: Minigun ammo, Rage, Minigun attack speed
Dakka-dakka-dakka-dakka-da-Kaboom-Kaboom!
You are the line. You determine how far the robots get. You are the centerpost of the MvM team's line. Your position determines everything.
The first upgrade you should get is, regardless of map is Round Penetration 1. It effectively doubles your damage right there on the spot. Since you aren't always on the front lines, your 5 damage shots turn into 10 when they hit the bot behind them. You don't need much more than 1 level of this, as its rare to see a long line of bots to make use of this expensive upgrade. Subsequent upgrades should be ammo (very very important), Minigun attack speed. On heavy projectile rounds, Grab Projectile destruction as it will do more to keep you and your team alive than any other upgrade.
Most maps, Rage is extremely important for crowd control. While it might not seem useful, pushing giants back, and the bomb carriers is extremely useful at keeping your front line. If the opportunity arises, raging on sentry busters is also quite good.
My thoughts on the Brass Beast vs Minigun debate: Mobility is better than the damage. You can avoid snipers while spinning a minigun, you can't when you have the brass beast. During tank rounds you'll run out of ammo quick and have to stop firing with the brass beast. With a minigun and proper dispenser placement you can just move away for a moment, and never stop firing. Also positioning yourself directly in line of the bomb and making full use of Penetrating rounds DOUBLES your damage over the brass beast. In my mind, there is no substitute for the Stock minigun in this mode. If you can't see your enemies, how can you shoot them?
For gameplay, make sure you never have to leave the line. On Decoy the spot is the right side of the main "hallway" near the stairs. On Coal town its at the top of the ramp to the right side. (The ammo box is your lifeblood here) And on Mannworks its dependant on which side the bots are going, on the ground (to make use of the armor piercing rounds).
Just remember, your medic is best served on the PYRO not you. Fend for yourself and fire from afar. Don't forget to get to point blank range on tanks. Every time you aren't doing max damage on a tank, Saxton Hale rips a kittens head off and drinks the blood from it's body.
The Engineer
Primary: Shotgun/PosmonSecondary: Wrangler
Melee: Wrench
MvM Job: Area Denial, Support
Upgrade Priority: Wrench Attack Speed, Building health, Dispenser range.
While I admit I don't play engineer very often, I'll tell you what I've seen done that makes for the best teams.
Dispenser placement. Should always go near the heavy. If he has to leave to get ammo, the line crumbles. Place your sentry near a full ammo box and rely on that instead of your dispenser. Once you begin upgrading dispenser range the line will become more flexible. You are the component to determine how versatile your teammates are.
Proper sentry placement is key. There are a few universal places, such as the top right catwalk on Decoy, or the top right building on Coaltown. Use them.
Make sure your teleporters are facing the right direction and slightly behind the heavy's line. This allows your team to get quickly back into battle. Two-way teleporters are useful but unnecessary.
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I feel this is the best setup for any MvM team, and when people follow these guidelines we tend to succeed with little failures. Just remember this is a team heavy mode. Communicate, and don't play your pet classes/weapons when your team depends on you.
