np
Also note that multiple pyros working together as a unit can cause huge damage and confusion, its quite amazing to watch. Three pyros using voice com and group tactics are amazingly deadly, acting as back breaking shock troopers. Even a well planned defense will have problems with all that napalm seeping into every corner, as well as the grenade volleys paired with the vision blocking of the flamethrower.
The wall penetrating IC spam can smoke out even the most dug in SG/sniper, as well as inflict some serious hurt on any engis trying to out repair your damage. Also note that a pyro that doesn't pick up ammo can withstand several EMP blasts, and since a pyro group is a suicide shock group, most likely with a medic behind them for the cap, you will have plenty of ammo to do your job. Alone a pyro tends to be an annoyance, but in a group their power multiplies through the roof.
Imagine three pyros IC/nap jumping right through the grate in 2fort, and causing all sorts of defensive problems while your speed capper squeaks by. The armor of a pyro means enemies must devote a large amount of their attention to kill you off. Soldiers come to mind here, as they will need to expend most of their loaded rockets to deal with you, thus making them resort to the shotty when you call in the capping team. Thats a huge tempo advantage if timed correctly. Thats assuming of course that they can even figure out whats going on fast enough to make a difference.
Voice com is key to such an operation, as the cap squad must hit as soon as the pyros begin razing the defenses. If you mistime it, you are gonna have problems. Go too early, and the cap squad will get beat up by the dug in defenses, go to late and the defense will have had time to load up and get their head on straight.
Of course this is just one of many tactics a pyro team can use, I'm sure you can think of many more. Simply put, never disregard a skilled pyro as a threat. When someone gets involved in combat, they mentally begin organizing combat threats. The main classes that get a back seat are scouts, pyros, and possibly a spy out in the open. That is a key mistake in pub play, take advantage of it when playing pyro. In match play, well, no one is ever off guard unless you make them that way, which a skilled pyro is more than capable of.