Reason Why Ninja Tabi Seems OP
There is way too much burst so the 30 armor is extremely useful in stopping lethality from doing true damage to you. The passive is also extremely important since most lethality users use a lot of autos to kill a target, and that isn't the purpose of lethality.
Lethality is supposed to help you do damage with your abilities since your abilities have a scaling while auto attacks do the amount of damage based on enemy armor, and your AD, which is always increased by the AD of the items you buy. Because of that scaling issue, abilities need armor penetration because they can't be enhanced by any other means, but AD can easily be increased with crit.
However, most people using crit are using that as a form of sustained burst with a tradeoff that is fundamentally flawed anyway. If we actually had AD carries like Ashe, then armor would actually have some meaning. They would take some time to kill you, but they will eventually be able to kill you.
However, most other AD carries just have sustained burst. They do 650 damage per auto to tanks, so tanks are useless in the late game except for their CC.
What we should do is just rework crit to actually bring on sustained damage, and rework lethality to just enhance your abilities instead of nerfing item after item, just to have a 5 carry comp.

and any of the MANY items these build into.
or
are good for them. Any support can build
. Many AP mids/bruisers (even some assassins) build
. Any tank can build either of the things out of