Like shoting spies with the shotgun as an engineer instead of getting rid of the sapper first, all  it depends of the situation. There are moments w + 1 is very effective and I dare to say, fun.

However, there is a time and a place for everything, and going head-first on half-enemy team isn't one of these times.

Still... I've seen a lone pyro kill a couple of soldiers / demo with medic support. Sure, it was awful play of the enemy team, but what can I say? What works, works.