Scribble said:
In my opinion though this happens in every edition. To me it tends to be more of a function of the player personality thren anything...
Try playing a 1st level commoner in a band of 12th level PC classes and then tell us that balance doesn't matter.
Balance is complex, and is affected by the style of campaign a DM runs, but it does exist. Players generally don't choose character types that won't be that effective. How many Half-Orc Sorcerers do you see in 3E? Not that many, right?
D&D (and Magic) caters to a wide array of player types. In general, they all want their game choices to be effective - not always "killer", but will do the things they want them to do.
However, their definitions of what is effective differ.
In Magic, we talk about "Timmy", "Johnny" and "Spike".
"Timmy" likes having big creatures and powerful spells. It's all about big is better. Killing someone with a 12/12 creature is much better than killing someone with a 2/2 creature. In D&D, Timmy plays a Half-Orc Barbarian or a Sorcerer who maximises their fireballs.
"Johnny" is more interested in the concept. Winning is important, but it has to be done with style. It's much better to kill someone with a swarm of 200 squirrels, lovingly assembled over 20 turns, rather than just go the obvious route. In D&D, Johnny probably plays something like a Bard.
"Spike" is just concerned with winning. Spike doesn't care what methods he uses, but merely with having the most effective deck - most likely copying it from the internet. In D&D, Spike probably plays one of those overpowered Clerics that gives the class a bad name.

Alternatively, check the Order of the Stick. Nale (Elan's half-brother) is a Spike. (See the conversation where Nale explains his multiclass combination to Elan...)
Being D&D, the types don't match entirely, and we have more (because our objectives are far more wide-reaching), but the basic idea remains: there are many different player profiles that play D&D.
Magic has been so successful because it offers people a range of choices about how to play it. You are not forced into one style of playing it. Tournament (Spike) play is only one style, and there are many who play it just casually, seeing if they can get their Weird Theme decks to win...
D&D, as it has progressed since its original release, has been about offering players more and more choices.
In 1974 you could play only three classes: Fighting Man, Cleric or Magic-User. In the first supplement, the Thief and Paladin were added. The history of D&D has been about more and more options.
Unfortunately, in 2E, the options trumped Game Balance. Options are popular, but there was no quality control in 2E at all. Thus, you'd get absurdly underpowered options, and then the absurdly overpowered options. The Complete Elf, anyone?
3E was about creating a system that allowed players to customise their characters. The lessons of 2E were learnt, and learnt well. That's why we have Feats, Prestige Classes and a plethora of new classes.
I've seen expressed in this thread an idea that you can have a rules-light system that allows balanced optional rules to be added.
I wish someone could tell me what that system was, because in the entire history of D&D, optional rules almost invariably favour one class over another. The change the balance of the game.
A new feat also changes the balance of the game - but, in most cases, the effect is much smaller than the optional subsystems that the feat system replaced. As the game progresses, the effect gets smaller and smaller because there are already so many effective options. Is there a feat a 4th level fighter would prefer over Weapon Specialisation? Probably, but it isn't a given. As the feats are generally balanced against each other, choosing between them is of consequence.
I discussed earlier the three player profiles for Magic. Did you know that Wizards designs cards with all three types of player in mind? Some cards in a set are for Spikes, some are for Johnny, and some are for Timmy. There are cards that overlap, of course.
I'm sure that the same is true for D&D, though without a Mark Rosewater in the D&D design team, we don't learn about it. Although there's an eye to keeping the classes balanced, there's also no doubt that they're looking to keep different styles of player happy.
Incidentally, I'm primarily a Johnny. I love using 6-card combos in Magic, and I play Bards in D&D.
Cheers!