Including rating in the league leaderboards would defeat the purpose of the league system. One mayor advantage is that it abstracts away the intricacies of trueskill rating. People gaining seemingly random amounts of points after a game, new players looking like they have an established rating, yada, yada, yada. On top of that the league leaderboard is not necessarily sorted by rating, making it even more confusing if we displayed the rating there.
Having a rating leaderboard somewhere on the website is a different story, but in the client it doesn't fit.
Global was given no league, because the rating is too unreliable. I can understand the desire to look up people's global rating, but implying a ranking in skill by putting them in a leaderboard in descending order feels off for me.
Not sure how useful win percentage is, the win streak and last game played info seems pretty nice