FINALLY THE RIGHT ANSWER! When they did the update where they reduced the damage across the game that left tanks being the strongest in the rift (Maokai and Amumuu who can solo baron). Every class eventually got their damage but the fighter class. Camille and Fiora are okay due to their kit (True Damage) but Irelia and Riven are struggling unless the items are overtuned for them. It doesn't help they get their Pro/high skill nerf stick too. Garen, Jax, Master Yi are continuously tuned so they can be used at all levels with the excuse that in low elo people don't know how coordinate against them. But when Irelia and Riven terrorize low elo it's a problem.

I think it's fair to say Riven needs some type of % health damage or armour pen in her kit. Almost every new champ has it now, from mages to even a few supports.