They've had their fun
It's Riven and Fiora's turn for the next 'wave' of nerfs in the top lane. Originally when Top was becoming more and more part of the meta a lot of champions were seeing the nerf bat. Zac, Dr. Mundo, Shyvana, Renekton, Irelia (lol so sad at this point :S), Darius, Rengar, Rumble, and Singed have all received balance changes to better suite them in the game, they all offered too much in team fights or were too strong on their own. Currently Riven and Fiora fit perfectly into this situation and I believe it's their turn to receive balance changes. Out of all the champions I named above, only Rengar has had the ability to do what Riven and Fiora can do, take on multiple enemies at a time and come out ahead before dying, but with the exception that his changes don't allow as much burst as he used to do.