Humm, I tend to agree with what what have determined was the original thesis of Driddle's post. That is that certain of the classes have too narrow of a focus/progression. I've felt this way about the Paladin, Druid, Monk, Barbarian, and even Cleric. This isn't to say that these are badly designed classes, I've just felt that they lacked some flexibility in their overall concept and roleplaying/rollplaying potential. I realize that the idea is that you give up some flexibility for unique/special abilites, but do these classes really need such a narrow definition. Would allowing some diversity "unbalance" them so greatly?
Consider which are the core classes in D&D that are most commonly seen in campaigns. I've seen more Fighters, Wizards, Clerics and Rogues than Barabrians, Monks, and Druids. Yes, this is the way the game was designed, but I also think that some of the flexibility issues are at play here.
Consider the Barbarian. Must all barbarians have anger management issues

and be speedy. When I think of a Barbarian, I think of a Fighter whose main ability is his Constitution and not his Strength. Given the extra hit points, rage bumps, etc, I do not think this is too unreasonable an intrepretation, but I'm certain some will disagree.
Consider the Paladin: Must they all be holy fighters devoted to some diety? Could they not be devoted to some cause. Maybe they should be Fighters with minor divine spell casting abilites, and differentiate them from there.
Consider the Monk. Must all monks be Asian influenced unarmed combat specialists seeking perfection of body through mind. Not that this is a bad concept, but I've noticed on the boards that many people consider the monk class a poor fit into their campaign. Could we not come up with a more general concept for the monk class. Perhaps we should just define monks as unarmed combat specialists and go from there. Or perhaps we should define them as combat specialists that combine wisdom with their fighting style.
It seems that if we had a core understanding of the base mechanic of these classes, then it would be easier to design out alternate feats that different versions of these classes would get at each level. I think that since these classes don't have a base definition that revolves around a base attribute, then they end up being versions of the core classes with narrowed paths and some more goodies.
Aside Rant
It's has stuck me that some of the core classes just seem to be subclasses of Fighter or Cleric. Too me, I've always viewed that the class design should have been based around core attributes. For example, the design could have gone and almost did go something like this. We have the Wizard, their primary attribute is their Int and they cast arcane spells. We base their spellcasting around this and their skills. Next, we have the Sorcerer, their primary attribute is Charisma and they cast arcane spells. Fighters are mainly Stength based. Clerics are wisdom based and cast divine spells. Rogues are mainly Dex based with lots of skills. Barbarians are say Con based.
Now what is a Paladin? Perhaps they are a fighter with minor divine spell casting ability. Perhaps we build in that they champion a cause- whether it be a diety or an idea. They can get more specific feat chains that a fighter, but still have the opportunity to diversify. Perhaps we make the Monk a Wisdom based fighter.... Maybe we should have a Fighter with minor arcane casting abilites, kinda like old 1st ed Rangers. You can go one from there.