There are any number of ways to categorize the classes...and where what lines are drawn for whom is really an individual and subjective taste/preference thing. How detailed or general things are, how many classes are too many or how many we need to start with, what could/should/would/will be a prestige class or a specialty/tradition/domain/style/scheme/college/grove/guild/company/order/etc/etc/ad/infinitum.
Not to suggest or desire any connection to 4e-style power sources, but just as an organizational tool, here's a couple of ways I generally look at these things...
General/Broad: ("the Big Four") Fighter, Rogue, Cleric, Mage
Specific: Ranger, Assassin, Druid, "Specialist Mages" (and one can argue which are more rare than others per setting) and/or Sorcerers...Barbarians and Warlords if you use them, I'd rather they be done through background and specialty, myself.
Rare: Paladins, Bards, Shamans, Warlocks, Monks
OR you can go like this...
Where Warrior classes = primarily Weapon focused, Expert = primarily Skill based/focused, Magic-user = [obviously] primarily "Spell" based/focused:
. . . . . . . . . .Warrior. . . . . . .Expert. . . . . .Magic-User
Martial. . . . . Fighter. . . . . . .Warlord ?. . . . .Sorcerer ?
Arcane. . .Swordmage ?. . .Specialist Mage. . .Mage/Wizard
Divine. . . . . .Paladin. . . . . . . Monk. . . . . . . .Cleric
Nature. . . . . .Ranger. . . . . . .Bard. . . . . . . . .Druid
Stealth. . . . .Assassin. . . . . ..Rogue. . . . . . .Warlock
again, Barbarians and Warlords not really my thing, but you could add, in theory, Barbarians at "Martial/Warrior" or "Nature/Warrior"..."Spirit/Warrior" if you wanted to add a "Spirit" power line (for which I'd probably make Shaman the Spirit/Expert and Medium or Oracle or something the Spirit/Magic-user...or Monk the Spirit/Expert and Shaman the Spirit/MU..but I digress...)
Sorcerer and Swordmage could conceivably be swapped depending on whether you prefer/fluff one or the other be "someone who uses magic with/through their weapons and armor" (Arcane Warrior) or "someone who uses magic AND can use weapons and armor also/in addition to their magic" (Martial Magic-user).
In a general way...I agree with pretty much all sides of this discussion...
to the Original Post, yes, I do feel the backstory/fluff they have introduced for the Sorcerer is a bit toooo specific to warrant its own class. And transforming oneself as they loose willpower doesn't sound, to me, to make them any more appealing. But then, I have never liked the Sorcerer as its own class...ever. About as pointless as the elf/eladrin split in my eyes. No reason spontaneous casting couldn't have been introduced and added in somehow to the Wizard class' options.
The Warlock is, simply by definition, a very specific archetype. But somehow, the differences between a Wizard and a Warlock work for me/are separate (in both flavor and mechanics) enough in a way that I don't mind the idea of them both being classes...and that's coming from someone with a VERY narrow/specific idea of what/who Warlocks are.
They are flavorful. Yes. But do they a "base class" make? For one I say "Yay" and one I say "Nay."
So, again, it's a personal preference/individual taste kind of thing where that line is drawn between "too specific" or "too broad" or simply "I don't like/want/need it"...but that ought not translate into "don't offer it in the books for ANYbody".
But then I also see the desire for a full-bodied array of possible archetypes for players to choose from...and while I think the whole notion of 100 classes is a silly one, and personally do not desire to see more than 10 or 12, initially, out of the box ("paragon archetypes/prestige classes/advanced specialties/whatever they are termed" don't really bother me in theory...but the splats can get splatty verrrry quickly/easily.)
But, yeah, I can appreciate the "gimme more options" position. And, like it or not, Sorcerers are now around a decade (lil' more than?) in the game...can't really argue with that sorta traditional base.
So, while I will agree that the Sorcerer and Warlock are a bit too specific, even so far as to not warrant their individual class for some tastes, they are NOT one of the Big Four...and so, being "Not one of the Big Four" (what we old'uns used to call "sub-classes") I expect their archetype, in flavor and mechanics, to be more specific than a Fighter/Rogue/Cleric/Mage.
...did I answer the thread or just ramble on...I've lost track.

--Steel Dragons