It's mildly amusing to watch some of the little epicycles that occur in these discussions.
"You don't need the classes to balance, it's a cooperative game, everybody should be happy to see the party succeed...."
...to everything turn, turn, turn....there is a season turn, turn, turn....
"....this isn't a cooperative game, you don't need the classes to balance, everybody can be happy just doing their own thing."
Like, D&D has always been cooperative, with classes that could help cover eachother, even "needed" eachother...
(.... just, back in the day, some groups (and I feel like, from reading his stuff, EGG expected it), it was a combination of cooperating for survival and competing for the best rewards. Cooperative rivalry, maybe? )
Obviously, the big one was Cleric. You've always needed Clerics to heal you, but, it was always a less popular class. Post-TSR, you got more alternatives to the cleric, making the role easier to fill.
The Fighter has (or "martials" more generally) often been talked up for it's role in protecting other members of the party, especially in response to the martial/caster gap.
