riven's gameplay is too dependant on matchup
get a good matchup ... proceed to faceroll get a bad matchup ... pray for the mercy of your jungler and even that might not help
and i dont see her having many matchups that rely on her playing much better than her enemy ... most of them is either stomp or get stomped
in the end its hardly possible for riven to win a bad matchup and its hard for her to lose the easy ones unless you will find a realy pesky jungler wchich isnt champion dependant
in teamfights and onwards its the player that does stuff ... but early game your possibilities are realy matchup dependant i think that riot should emphasize her gameplay to be more reliant on a player than a matchup ... especialy for a champion with such a high outplay potential