The Pyro is another class that is pretty easy to pick up in Mann vs Machine. His best use is comparable to that of the scout. The Pyro fights on the front lines just as the Scout does, only with its focus on doing damage rather than grabbing the money. If there is no scout on your team then his responsibilities of collecting all the money fall to the Pyro. If there is one, then they must act as partners. Since they are both in the heat of battle, they are each others back up.
While the Scout hangs back then will run to the front, the Pyro should hide in one of the corners at the front. Once the wave starts while the Scout is rushing in, the Pyro comes at the robots from behind or the side. Each wouldn’t do much damage on their own, but together this tactic will take out a lot of robots, especially those that have a standard speed.
There are several robot classes to watch out for while playing as the Pyro. The first is obviously the robot Pyros, or their giant version. They have the same kind of immunity to fire that you will, so with them its best to hit them with you shotgun or ranged weapon from afar and don’t be afraid to get some help with them from a team mate. You should also watch out for the robot Scouts. They are more likely to run past you than to actually fight, especially if you are on top of the bomb. Don’t bother trying to chase them but instead just plant your feet at a choke point and try to burn every one that passes you. You won’t see them die but the continued burn will do most of the damage as they pass you, so they’ll either die or be easy pickings for a team mate at the base.
It’s for this reason that I recommend upgrading your burn duration and your burn damage on your flame thrower. This way you only have to light each robot you come in contact with. If your around the middle of the map, none of the regular robots will survive the rest of the walk to your base even though they aren’t being fought by any of your teammates. Also you’ll want to upgrade you ammo capacity. It’s really nice that the Pyro doesn’t need to reload, but the go through ammo very quickly. Especially if your using the compression blast. This has some pretty great uses. The compression blast is useful when the bomb is close to reaching the base to regain some crucially necessary feat. The most interesting perk of the compression blast though is that the player can use it to reset the bomb. If you blast the bomb carrier into the pit that is on the map Coal Town, the round will have to spawn a new bomb carrier at the front of the level, giving you a huge amount of comfort in some of the more difficult rounds.
The pyro is a great class in Mann vs Machine for a take charge player, leading their team into battle and able to give assistance where needed.
Article from Gamersyndrome.com