In our view personal competence is a 20th century value. Back then (way back all of ten years) success involved solving operational problems. Specialists solved most of these, either as discrete technical problems or as systems issue.
In the 21st century we have all been exposed systems thinking, some of us highly trained in it, and yet managing systems is even more frustrating because in addition we need Process Thinking. Our success now requires participation with several (even many) other highly trained and experienced people to achieve our objectives. Personal competency is necessary but not sufficient, process competency is now required. Process competency can only evaluated on the basis of the group which "owns" the process. This must be accomplished by evaluating the team as a unit and not simply by the evaluation of aggregate personal competencies. Just as a baseball franchise which "buys" the best player at each position does not guarantee a championship team !
Therefore Leadership is (or must now become) a process competency which empowers the team and is not simply the personal competency of one of its members.
As such, the team may rotate in the position of "leader" depending on the assignment and the needs of a situation.