Anti-true damage item
Hey , I was wondering what can happen if we had a tank item with a unique passive , that reduces true damage taken (10-20%) it wouldn't be a must build against flat true damage , but it will help against %Hp true damage cough fiora cough So instead of her killing me with 4-5 hits , she will have to hit like 5-6 vitals instead which will allow for some counter play in the "micro" aspect .

kinda already fills that demand already too. I wasn't aware of it previously since I haven't been getting around using that item myself.
would build
to be effective vs her. But at the same time he loses secondary stats as well as less efficiency vs AD/AP users (and becomes way more vulnerable to % hp PHYSICAL or MAGIC damage). However the fact that a lategame Vayne would murk Nasus no matter what he builds both in teamfights and duels doesn't seem very healthy.