Riven Nerfs Missing Key Issues
The new edge mechanic, though really interesting, is missing some of the key issues with Riven overall. Her ult is supposed to be the strongest part of her kit, an execute that allows her to be bursty and build mostly damage items. However, edge makes her ult more for extended skirmishing or using animation cancelling. While this is taking Riven in a direction that could be interesting, I believe that the change should be to her passive rather than her ult.
For instance, the three maximum stacks could be reinstituted and the damage could scale with the amount of stacks Riven has built up. If she has three stacks, the damage is reduced to one third of a maximum number and all stacks would be used, and at one stack it would do a base number with decent AD scaling which could be fiddled with in order to address the issues with her current kit. This would allow skilled Riven players to be strong without her ultimate, rewarding smart play and good mechanics; at the same time, it would discourage button spamming and make mastering Riven more rewarding than the edge mechanic.
Of course, this solution is theoretical but it does show my point. Riven's kit is too strong right now because she is strong with and without ult regardless of the mechanical skill of the player behind the wheel. As of the changes on PBE during the time of writing, the edge mechanic is clunky and making her identity confused and not great overall.