Darius is leader of Strength, Swain is leader of Vision....

...I wonder who the leader of Guile could be? ( )

######Guile : sly or cunning intellegence

Jokes aside: I don't think there's any other answer to who the last leader is. Guile is more about cunning but disguising and tricking opponents in turn can be considered cunning. I'm more or less wondering though if this means Riot may be planning a full rework for LeBlanc after some time of her supposed rework revert.