A little while ago, I started compiling the results of every team for almost every major tournament since the start of Season Two last November. After thousands of matches, I applied a variant of the Elo rating system to calculate the ratings of each team, and have kept this list up-to-date since then. You can read more on my methodology in this blog post. Let me know what you think!
You can filter by region by clicking on the little icon in the upper right of the Region column header. It's interesting seeing how the different regions are faring (with Asia being incredibly strong right now).
Click through the teams to see their match/tourney history, how they stack up against rivals, and a graph of their rating/win/loss history. You can see which teams are hot (e.g. Team WE, Fnatic) and which teams are slumping (e.g. TSM, Team Dynamic).