Corinth said:
The problem is that D&D 4.0 attempts to compete with World of Warcraft not by attacking the latter game's weak points, but by attacking its strengths.
First off, I don't know that D&D is "competing" with WoW. The two games fill very different niches. For me, D&D competes with going to a sports bar or bowling or some other group activity that I'd do in person with a group of friends. WoW competes with... well, I stopped playing.

But when I did play, WoW was more of a "zone-out" activity, like watching TV. This changes at endgame a bit, when you're spending 20+ hours a week on structured raids, but at that point WoW is competing with EVERY aspect of life.
In any case, D&D does need to play to the strengths of its genre, but there's no reason it shouldn't also take the best from other media, except when it's losing something important in the tradeoff.
Abilities that are available at-will, or have a one-encounter/one-day cooldown, mirror the way that World of Warcraft has most class abilities either on short cooldowns (which, if translated from real-time to tabletop play, are effectively at-will) or on long cooldowns (which, likewise, translate to per-encounter or per-day) and are focused upon practical use in a tactical combat or adventuring situation. (Abilities that are, for all intents and purposes, intended for use during downtime are minimized.)
To the degree that this is true (and it's really a bit of a stretch), this only really reflects on good design for tactical gameplay. If powerful abilities didn't have cooldowns or mana costs, they'd be "spammed" repeatedly (or in D&D, used every round). You need SOME kind of resource limitation on character abilities. Moreover, D&D has ALWAYS had a combination of "at will" abilities and "per-encounter or per-day" abilities. The only change here is that they're adding some less goofy per-day abilities for classes like wizards that were previously stuck carrying around a crossbow for when they ran out of juice.
The skill list, likewise, is reduced to those that have an immediate application in the adventuring context while those used more or less during downtime are removed and instead rolled into general attribute checks.
How is this like WoW? In WoW, the only skills of note ARE out-of-combat "crafting" skills. This seems like more of a generic "4e is video-gamey" charge than a specific similarity to WoW. But to address it: all 4e is doing is more rigorously separating out the combat mechanics from roleplay elements. I never needed skill points or feats to play a noble or a merchant-prince in 3e, so I don't know why I'd need skill points to play a cobbler or a lutist.
Something else to bear in mind about 4e skills: they're probably like SWSE skills, where the only difference between "trained" skills and attribute checks (with level bonus included) is a flat +5 bonus. If you've established in roleplaying that your character plays the lute, and you have a "perform check" to play in concert, don't you think your DM would give you a +5 circumstance bonus? Voila, your attribute check is mechanically EXACTLY the same as a skill check would be, and you didn't have to gimp your combat capability for the roleplaying benefit.
The classes are designed to fill necessary roles in an adventuring party and have no need for justification outside of this concern, regardless of whatever label gets tied to them. Defenders are tanks, Strikers are either ranged or melee damage-per-second specialists, Controllers are crowd control specialists, and Leaders are healers; this is a better-communicated version of the Tank-Healer-DPS Trinity of World of Warcraft in that crowd control isn't necessarily recognized as a separate specialty, but instead is acknowledged as part of the DPS role.
Thanks for not falsely claiming that WoW has "controllers," but you should still note that previous MMOs DID have them. It was an innovation of WoW to spread crowd-control out among all the DPS classes, rather than having one class responsible for crowd control like in Everquest.
ANYWAY, how do the classes "have no need for justification outside of this concern"? The idea behind "combat roles" is that every cool class idea can have its place in the party, so classes like the bard that were previously good for roleplaying but kind of superfluous in combat can now hold their own. Like it or not, D&D is and has always been a combat-heavy RPG, and a class's combat utility is very important.
The adventure design paradigm is one of a series of encounters, often linear in their design, that build up towards a master villain--the boss--
You just described not only all video games, but also most films and a lot of literary works as well.
...and each encounter has one hostile NPC per PC in the group as a baseline.
This has nothing to do with WoW, where the number of mobs a 5-man party might face varies from 1 to 20.
For all intents and purposes, a game setting consists only of Adventure Sites (the World of Warcraft equivalent, usually, is a dungeon instance), friendly towns (to do downtime maintenance and upkeep) and the occassional random encounter. (This feels more like Guild Wars or Dungeon Runners than World of Warcraft, but still an MMO influence.)
NPCs have set XP awards. Loot has level requirements, both to craft and to use.
PCs, by default, have no meaningful influence upon their surroundings. They are passive participants in their society and its concerns, as their actions have no impact outside of what's scripted for them.
Where are you getting these? It sounds like you're making gigantic leaps based on a few snippets from W&M and other sources. Heck, the last one seems to go directly AGAINST what I know of the implied setting. A level 30 D&D4e party can KILL A GOD, and he won't even respawn in a week!
What tabletop RPGs do better than electronic RPGs, or board games for that matter, is not merely simulation of a fictional world. (Computers do that better also.) Neither is it addressing themes through narrative conventions. (Books, comics, film, radio and television are all far superior media for such purposes.) What tabletop RPGs do that no other popular media allows is the immersion of an individual into a secondary world for the sole purpose of living out a secondary, parallel, life in a position and perspective other than our own--and in a historical specificity and continuity other than our own--and thereby allow us to experience--to live through--things that otherwise are impossible to know, be it the experience of living through the tragedy of Troy or the experience of living as a merchant mariner on a free trader far into the future, or something else entirely, for the expressed purpose of developing the minds of the participants through such play. This is what D&D's design--what all tabletop RPG design--should focus upon, facilitate and encourage.
(Note: The only other medium that can accomplish this is Classical Theater, as Friedrich Schiller notes in his "Theater as a Moral Institution".)
Thanks for the shout-out to my man Friedrich, but you should realize that (a) there are a ton of RPGs out there better suited than D&D to the "roleplaying immersion" mode that you're suggesting, and (b) they all sell much worse than D&D. So if the "only hope" for D&D is to become that kind of low-mechanics heavy-RP system, that's really not much of a hope at all. As I hinted at early in this post, a lot of people play D&D purely as a social event, and the combat mechanics are what helps make it fun FOR THEM. (Speaking for myself, I sure don't mind roleplay-heavy games at times, but sometimes I would rather slash through a few orcs and steal their gold pieces than lament the death by Martian Flu of my half-biotic godchild aboard the Starship Futura.)