As an Old School DM I don't use the concept of balance at all in a game. Balance as a game design thing is just silly. Ask anyone to "balance" and they will do so. Some might agree to the "balance"...but some, maybe most won't. Balance is an unattainable goal.
A lot of balance problems that people have are because of play styles. People play the game one set way they choose, and then find that way disrupts ("unbalances") game play. But when this is pointed out to a gamer, they will simply ignore it.
The classic example:
At a high level, past say 10th level characters might encounter a flying ghost like foe. A mundane fighter that can't fly and has no magic at all can't do anything in this combat. So the player will just sit and do nothing. Many will say this is normal and acceptable and part of the game, while also saying they greatly dislike this. But as this is made into the rules, most feel nothing can be done.
At high level, say past 10th, characters might encounter an anti-magical glade with savage foes. The high magic spellcasters can't do anything in this combat. So the players will just sit and do nothing. Except here nearly everyone will be screaming that not only is this wrong, but it must never be done in a game.
So, why the difference? Why is it that doing massive negative things to a mundane character so they can't even play the game perfectly fine. But even the idea of doing anything to effect spellcasters will never even be considered?
Why is it fine to say to a player of a fighter or rogue character to just sit back as they can't play the game for a couple minutes? But it's unacceptable to tell the player of a wizard or cleric that they can't play the game even for just a couple seconds?
And that is one of the big "balance" problems right there. But the problem is the decisions of the gamers, not the game rules. Everyone plays the game how ever they want and that is all good and fine. But when you only drive your car on a rough rocky roads and find the ride quite bumpy....you don't stop and say that the cars tires must not be balanced.