The article stresses some good points, most of them showing up in HBR every now and then. However, the environment (esp. of a "freshly" promoted manager) can also be at fault of the underutilization and overwork.
Coworkers and subordinates quickly spot other employees that are the "go to" people. What you need to be able to do, is to say "NO, do it yourself" in all but the most important cases. Give directions not solutions, delegate.
I found One Minute Manager to be a good book on the topic, illustrating the problem very well : http://www.amazon.co.uk/One-Minute-Manager-Ken-Blanchard/dp/....
Coworkers and subordinates quickly spot other employees that are the "go to" people. What you need to be able to do, is to say "NO, do it yourself" in all but the most important cases. Give directions not solutions, delegate.