Janna changes
As it stands, Janna's place in League has dwindled. Other people simply do what she does, but better. Thresh and Karma provide better escapes/peels, do better job of singling out an enemy, and have as much presence in a team fight.
Beyond that, her role in team fights is confusing. Obviously, she can reset a team fight with Monsoon, peeling their team off of your team, but she doesn't really help if you are ahead, besides using Eye of the Storm on your ad carry. Also, in terms of her positioning, she is a champion that needs to be with the carries, to maximize Monsoon's effects and the ability to cast Eye of the Storm. Her offensive cc, however, requires her to be a mid range champ. This is because of the tiny range on Zephyr, and having to choose between not being able to hit enemies with Howling Gale because it didn't have range because you used it too quickly or not being able to hit enemies with Howling Gale because they noticed that it was building up, and simply walked out of the way of it before it went off.
To make her better, I think that changes need to be made to both of these abilities. With Howling Gale, remove the charge up, give it power and range somewhere in between a full charge and a zero charge Howling Gale. With Zephyr, increase the cast range by at the very least 100.
I think these changes will make Janna a very good backline support.