I disagree with most of his assessment. The current WoW team has changed some of their practices, and is experimenting with new ones, but I would argue that the current design team is the most successful, and that WoW is in far better shape than it has ever been because of their efforts.
Eric tells the following anecdote about Asheron's Call 2:
I found that the Feral Intendant class was 30% overpowered, and that’s why so many people were playing a Feral Intendant. Yet somehow, reducing the power of the Feral Intendant to the correct level did not suddenly make the game more fun… thousands of players were complaining and nobody was telling me they were happy about the change. Weird! I double checked my calculations. They were correct. So what had gone wrong?
Turns out that the people who played the other classes available to that race had taken on an “underdog” mentality. The people who played Claw Bearers liked that they were woefully underpowered compared to Feral Intendants. It was like playing the game on Hard Mode. And the people playing Feral Intendants liked playing on Easy Mode. In balancing the game I had failed to understand the needs of the people playing it. I just ham-handedly fixed the equations, instead of solving the problem with the finesse it needed. It was one of my more serious missteps. (And it’s a great example because I think it’s pretty obvious in hindsight. Most mistakes were much more subtle.)
If memory serves, AC2 was a failure, and didn't really last long enough to develop a significant endgame. All this talk of "Easy Mode" and "Hard Mode" goes out the window once people stop getting invited to groups because their class is underpowered.
Then you see how important class balance becomes. The point of MMOs is to play with other people. If other people refuse to play with you because of your class, your game has failed at a fundamental level.
By that measure, the current Live team has done a superlative job. Pretty much every spec for every class is respectable in the modern PvE game. That is a massive difference from the situation during WoW 1.0. If you now want to play as a Enhancement melee shaman, go ahead. Survival Hunter, why not. And each of these specs are reasonably different from each other. The current Live team managed to make Discipline priests both viable and play differently than Holy priests, which is nothing short of a minor miracle.
As an example of how much better the game is, last night I got to DPS as Retribution on our guild-first kill of XT-002 Hard Mode. (I was pretty terrible--lol 4k DPS--but it is my secondary spec.) In 1.0 and TBC, I would not have been able to play as Retribution as my primary playstyle in optimum gear, let alone in mismatched leftover gear. I would have been forced to heal. Now, I heal because I choose to heal. For that alone, I think that the current Blizzard team is doing a great job.
It's not just class balance. Ulduar is a superb instance. It has a large variety of bosses, interesting trash, complex fights, and challenging hard modes. It is quite possibly the best instance ever released. Even the hotfixes have improved the pacing and tuning.
I do think Eric has some good points, especially about the fact that some changes are not "clean" enough, and the fact that tooltip changes lag behind hotfixes. Some of the current Live practices could be improved. But I think he is focusing on smaller flaws, and is missing the very large advantages that the current Live practices are bringing.
The current WoW team is doing many things differently from the original team. Changes are coming faster, and they are more open about current and future plans, even if those plans end up changing. Sometimes this makes them seem more fallible, but I think they should be judged by the result. And the clear result in my view is that the current game is leagues ahead of WoW 1.0 and 2.0.