Specifically targeting leadership may not have any appreciable effect for, as your links show, someone else will rise to take the reigns.

However, I have seen good arguments for killing insurgents. From what I understand, there has been some achievements in areas like Kandahar and Helmand where area denial and plain ole' attrition has insurgents reeling tactically.

That being said, tactical victories are only part of the equation - strategy is about convincing the enemy to quit pursuing his ends and if you can't get that right, then your tactical victories amount to nothing.