I disagree. As you level you gain new abilities slowly as you move up the ranks. This allows you to learn your abilities and become a better player overall. If you don't have that period where you're learning your abilities, you just flop around until you figure things out. Heck, using your argument, why have levels at all? Lets just start everyone at max level.
I also think you just don't care about a class you start at a high level. At least, not as much as a class you take from level 1-90.