I think this is a very good point, and I'll be rephrasing the pledge a little bit later to account for this. While general leadership philosophy basically echoes what you said, and while tanks are naturally and mechanically the leaders of the group (in that they literally lead the charge), it's very easy to take the idea of "leadership" as meaning "I automatically assume that because I am a tank I get to autocratically make decisions about how the run will work." Instead it ought to mean "I understand that my role as a tank puts a mantle of leadership on me, and gives me a greater responsibility to be sensitive to the needs of my group."
EDIT: I modified the phrasing a bit - do you think that makes it a little better?