Riven and Fiora

is useless unless she's fed.

just build armor early game, you can outsustain her and hit her with your abilities once her combo is over.

Any justification for why they should be nerfed?

Just because you don't know how to play against them is not a reason for them to be nerfed.

Riven has no manna. That should be fixed immediately. Her cool downs are super short. She has 2 gap closers aoe stun and ult that when fed destroy teams. Oh and a shield. You could literally undo all the previous nerfs and just give here a manna pool and I think she would be fixed. I'm am sick of seeing a riven with lifesteal and cd boots staying on field all game until she.

1 Super farms 2 Gets fed

As of now she is STILL op.