Armor penetration

So, with the changes to the last whisper and it's newly introduced upgrades.. They are only working on bonus armor but what about the base armor values? What about the assassins? An assassin's job is to kill the nemy squishies as fast as possiblebut when everyone has 80 or so base armor and you only work on bonus armor, you need a lot of flat pen to actualy do your job. And when i say a lot, i mean a lot.... You need a fully stacked black cleaver, a youmu's ghostblade, 19 flat armor pen in runes, a last whisper upgrade item in order to do what you could do with last whisper as it is now, a youmu's ghostblade and your armor pen in runes... so now, in a teamfight, you need to go face to face, hit them 6 times do all your damage and only then will they have an effective armor that let's you do your job... In a 1v1 skirmish, it could do the job, but in a tamfight??? what are we supposed to do? And, ok, there is some flat armor pen in masteries, but that's just 8.4 at level 18, and to get that, you need to go full utility tree and no offence... So.... what exactly arethe assassins supposed to do? Either make an item that works on total armor and make it available only to the assassins if you think that Marksmen will be too stong with it, or add more flat armor pen... And mages still have that void staff to go through all of the opponent's magic resist on top of everyone having ridiculously low base magic resist value of either 30 at all levels or 53.4 at level 18. Marksmen are supposed to be easy to kill if you get close to them, but not graves... 30 armor stacking up to 4 times from true grit and stacking instantly with quickdraw? So, at level 18, with scaling armor runes and a he gets 275 armor.... That is 3 armor more than a garen with a , a , a a fully stacked W and 9 armor seals at level 18. RIOT PLS!!! What is this??? Riot pls, how is this in any way balanced??? an ADC with only 1 defensive item having more armor than a tank with 3 core items??? Is this realy "balance"??? is that what you call "healthy" gameplay and stats??? Oh please...