When will Riven actually see a substantial nerf?
She has insane early game, insane mid game post-level 6, and insane teamfight.
Her mid game is pretty meh, her bases tapper off and her big-ticket items are not in her inventory by that point. You can 1v1 her with most fighters at that point and do ok, or simply dominate her with some others.
The only aspect of mid-game that really benefits Riven is that, as a duelist, it's nice that towers having fallen allow decent map-movement and team-fight formations aren't that common, so it's the best time to force 1v1s outside of just trying to take on your lane opponent.
Also - her team fight is terrible.
Riven's only defensive mechanic to justify being a glass-cannon is her Valor shield, which just about any CC will prevent her from using. Compare that to Fiora/Yi/Fizz being untargetable, Kayle being invulnerable (and ranged, and having the capcity to turn anyone on her team invulnerable), Jax being immune to auto-attacks, or Poppy being invulnerable and immune to CC: all these champions, as fighters, also have lackluster team-fight pressnece, but they have more reliable survial mechanics than Riven.
Riven's mobility also sacrifices a significant amount of damage should she actually need to cover, say, 550 range - as she can easily burn through 2 Broken Wings casts without even hitting anything on that journey - not to mention everyone can see she's coming and do something to stop her.
Most fighter/assassins with some level of mobility operate more on the 1-dash that sends them 650 range at their target in an instant, basically guaranteeing they'll land all of their kit's damage in an instant with minimal warning.
If Riven doesn't garner a significant lead - she can easily become dead-weight in a team fight. She's a melee-range glass-cannon.
She has insane early game, insane mid game post-level 6, and insane teamfight.
I'm not seeing this post as a solid break-down of a champion being insane.
It's much more a "QQ I was beat by Riven and am now salty about it" kind of deal.