I don't agree. Each class does it's primary function better than the wizard can possibly do it. In football each position has a unique skillset, but there is some overlap. Tight Ends and Running Backs both block a lot. Both catch the ball, but TEs do it better, but not as good as the WR who doesn't block, but specializes in catching. The WR also occasionally runs the ball(end arounds, though technically a catch, is more of a running play) and very rarely one of those positions will throw the ball like a QB.
All the classes are famous at their positions.
This part of the discussion was following ECOM3's position that the Wizard is in fact more powerful than other classes but the game is better for it. I position I haven't seen that often, and was curious about what it meant!
If you believe there is no gap than we are back to the other discussion...