Riven needs some buffs to be viable
Her passive is anti intuitive, forcing a caster to auto-attack is bad design. I suggest that her passive is changed to:
Runic Blade: Riven deals true damage equal to 25% of the enemy current health over 3 seconds every time she hits them with an ability, the effect stacks indefinitely.
This change is also good as it will decrease her skill cap (no need to cancel animations anymore), making her a viable choice for noobs and pros alike. Being overall a healthy change to the future of League of Legends.
Thanks for reading!