I personally feel that Riven should have her scailing on her E shield reduced, removed or changed. It is stupid in my opinion that a champion can go full AD and be extremely hard to kill because of a huge shield that comes with a dash to get away.
It's so she doesn't get instagibbed when commiting to an all-in. Her shield is designed to take one large instance of damage late game around 500 or so if you build her correctly. That's like 1 spell from a burst mage in a 1.5 second window that will be refreshed 3.5 seconds later (with maximum CDR) which gives plently of room to blow her the fuck up in a lategame teamfight. You could nerf the ratio but that would significantly hurt Riven's lategame carry potential. Which doesn't make sense considering she's a carry champion that's meant to scale the longer the game goes on (who would've thought?).
The shield scaling is so that if she's behind, you won't feed when you go back to lane as fast as the Yorick + GA bug. And you usually wouldn't go full AD glass cannon on Riven, especially if you max 'E' first as you only max E first if you don't think you're going to win trades/you're against a hard counter (e.g. Garen, Pantheon). You could nerf the ratio but that would hurt her more than the juggernaut rework did to the league community, considering the fact that the current masteries don't synergize with her kit that well compared to other top laners. If you do remove the dash, then that means she can shield herself during a snare, and even though that would kind of help her, having the dash always helped Riven players escape a gank to make up for her innate squishiness early and her horrible health regen.