Riven's cooldowns are far to low to allow any windows to catch her and kill her.
As much as I hate Riven's mobility and CC being that mobile and strong on a resourceless champion has to have a trade off (an exploitable one at that). Scratching 5 movement speed off her was basically a joke of a nerf. If Riven truly is fine in her current state in the damage and mobility department something needs to be done about her stupidly low cooldowns. And once she gets a single CDR item there is no hope when it comes to stopping her top lane snowball.