Balance. Why do we need it?

[ryu]

I think to most people, Balance would mean being able to contribute very well in your class's specialized area or well enough in several areas (like a bard), as well as having potential to be helpful outisde that. The problem is 3.5 is (unintentionally) not built that way. As many have pointed out: if you want to be a good fighter, pick a differeny class. And that's in their area of supposed expertise. Outside that, most fighters aren't worth their weight in guano

Edit: to be clear, this applies to most martials. 9th level casters tend to have the inverse problem: they can potentially do anything or make doing that thing irrelevant.

Even among t1s you have specializations in the sense some classes expend less effort or more effort to perform any given task. It's less about physical capability of doing any given necessary thing and more about who has the simplest time of doing it.