Big numbers of a single class on a team
Is there any good reason to have more than 3 representatives of a class in a match?
I'm
not talking about those occasional points in maps, where it might be advised (Scouts in the beginning of Fastlane, Medics on a PL-map etc), but the class-layout in general during the lifetime of a map.
One could say: If it works, why not having 4 demos or 5 soldiers or 7 snipers (

)?
But I dare to state that given equal skill level of the players it won't work.
IMHO TF2 has a quite good balance between the classes, which means that each class has a weakness which can be exposed by another class. So a good mixture of classes enhances the overall strength of the team (of course with variations depending on map and role). In opposite, concentrating on fewer, perhaps even similar classes introduces a weakness.
One good example is something I have seen over and over again, and again just yesterday: Dustbowl, Goldrush or similar, defense featuring 4 engineers. In 9 out of 10 times this won't work. Chances are, you won't get your sentries up to lvl3 (unless you work together, but then you will not have 4 sgs). The initial ubers will most likely kill 2 of the sentries. And once your sentry is down you start struggling to rebuild it. If for no other reason than because there are probably not enough other players to protect you, while you are rebuilding.
When I referred to "similar classes" above I meant that in most cases the team will profit from a good mixture between light and heavy classes. Here as well I have seen teams devolving to scouts, medics, snipers and pyros without a heavy class. This might work on occasionally, but most likely it won't.
Don't get me wrong: The class-layout of a team is a dynamic process which requires adaptation all the time. But there is a reason TF2 has 9 classes. TF(2) is built on those classes as a concept. Ignore the concept and you proof, that you don't understand the game.
Hmm, I admit this is more the kind of rant I did in my old editorials on the Fort than just asking for opinions. Still I'd like to hear what you think (especially since many of you have a different POV regarding clan matches)