Here is a video of duping and its detrimental impact on the game:
You fixed the invulnerable wizard bug in what.. a couple days? identify the bad code. Change it.
I agree that the game is not irrevocably broken... yet. But unless this issue is addressed it will become exponentially more problematic and ultimately unmanageable.
If we care about this game (and its longevity) we have an obligation to encourage Blizzard to take action. Any bloody action.
EDIT: For those who like duping: If you truly believe the game would be more fun if all gear were available and free then I just dont know what to say to you because you are really beneath the bounds of reasonable communication. I don't argue with children for a reason.