If Ninja tabi is unhelathy for ignoring 12% of auto attack damage
Then where does that leave Last Whisper, Black cleaver and Lethality which ignore or remove armor to a much much greater extent.
First we have Black cleaver which can Reduce up to 30% of total armor which is an effective team wide boost to physical damage. Then we have LW ignoring 45% of bonus armor without any conditions to apply. Last there is Lethality ignoring a flat amount of armor also requiring no conditions to apply.
If an item reducing auto attack damage by 12% is too over bearing where does that leave reducing 300 armor to 210 followed by the remaining 120 bonus armor being ignored to 66 and the reaming 90 base + 66 bonus getting farther ignored by 30?
That is 126 out of 300 renaming or 58% of armor begin ignored. There is no way around this armor pen/reduction. Once someone has it all you can hope for is CC to allow for their deletion before they can do much damage. Luckily there is an item to help counter CC and even provides leathlity...
And people are getting angry about the reaction being an item that is not countered by this large amount of armor pen/reduction due to it defending against a form of usually physical damage as a % reduction?
Ninja tabi is a symptom of a problem, Ninja Tabi is **NOT **the problem.
This champion is intended to protect aginst sustained damage.
This champion is intended to protect aginst burst damage.
This champion is intended to protect aginst true damage and percentage health damage.
this item
these items
(a commonly built item might i add)

is my go to main, but I also enjoy playing
mainly because she's been turned into one by mistake on Riot nerfing her a particular way. Then there is
who is labeled as a tank but doesn't really have the qualities of one. Will probably be reworked to better suit the role eventually.
this bad boy does a LOT of work people dont seem to give it credit for.
to be mentioned lol.
is damn near unkillable ;-;
and meanwhile 
which is 14.8 gold and 380 bonus armor