penetration needs to be nerved

when 5v5 u gotta tank not only ad or only ap (can happy but chances are extreemly low) the job of a tank is to take hits to protect his tm, not to get one shoted when scouting around lol, u guys might think i am overdriving but i am honnestly not, when u have around 350 ad armor and 300 ap armor, u oughta have like around 70% ap and ad resistance +-, this is suposed to be gud, however theres a item that reduce that procent for ad and ap res by 45% +-, think bout it, if 5 people buy armor penetration for ad and ap, this means that when full geared u only have ad and ap resistance like 25%, thats 1/4th of the total dmg, this means if enemy was able to deal 1000 dmg only 250 gets reducted while u have 4k hp, if all 5 players gonna do this, then one hit of those skills will be 750*5, thats 3750 dmg out of 4k hp, thats almost one shot, tanks arent meant to be one shotted, this makes tankes useless, theres no such thing as roleplay where tanks easly get outroled, tanks are meant to protect theyre tm, not to die instantly, i do see pottential in armor penetration, but 25% res out of 1000 dmg, is no such thing as tanking, let stand there are champs already dealing true dmg by max hp on %, so this is my explenation, not to delete armor penetration, but to nerve it so tanks cant be one shotted, tanks have to look at ad and ap res, but thats hard if there is ad and ap penetration, it needs nerv, its impossible to tank this way with only 25% resistance out of 1000 dmg