Let's clear something up, right here and right now.
Are you ready?
Setting down? Don't worry, I'll wait...
Good? Okay. Brace yourself; cause these words you may not like hearing.
There is no such thing as a 'balanced party.' Not in the sense so many people think of them. Don't believe me? Well let's do a little example here to illustrate my point. Imagine if you would a 4 person party, and let's say this party is one with the simplest form of balance possible - 4 fighters. They're all the same level, same race, and we won't even consider feats/skills etc. Now, you could say that you have a party of 4 identical characters with zero chances of being unbalanced. But here is the curve ball of a point - each fighter has selected a different weapon as their only difference. One may have taken a longbow, one a greatsword, another a mace and shield, the last a pair of short swords.
Even with such a rudimentary group we already have a unbalanced or 'un-fair' element many would declare as foul play. For instance if the fighter with his long bow gets his turn first some foes might be eliminated before the others can get in close enough to fight. In contrast if the foe is too big or is already in too close he might feel not feel effective. Is this party unbalanced? No. Because no party should be gauged against each other, they aren't battling one another. Instead the party is a team and as a team their effectiveness is the sum total of all of the members and how they act in concert against a foe.
A wizard may be powerful in regards to his spells but that is a limited resource that once depleted leaves him vulnerable. The fighter may not be limited in regards to such a resource but it is him who can protect the wizard and enable him to work his magic. You don't bench part of your team because their skill is beyond the others. No, you try to place your players where they are strongest and allow them to maximize each other.
Think about it. And while your at it check out this article with more such points to consider. A game is about having a fun enjoyable experience. If everyone does end up with such an outcome then that is what matters. Isn't it? The only balance we should worry about is between the players and the opposing team(i.e. - monsters etc.), right?