Too much armor pen in the game.
Armor is such a worthless stat right now.
Lets do some math.
sunfire, randuins, thornmail, deadmans, ibg and ninja tabi. thats like, the perfect armor tank build, it give tanks sustained damage while they survive a all ad team. lets use malphite as the tank here.
His base armor at level 18 is 100.8 so lets say 100 These number will be listed in order of the build above starting with base armor 100
100 + 80 + 60 + 80 + 60 + 65 + 20 = 435. and that is a full build malphite one of the takiest armor champ in game.
Now with just 2 items that number gets nuked down to 178.35. Then add in lethality which caps at 64.
That leaves us at 114.35 armor at full build against a assassin. They just negate 300+ armor because "lul %pen"?
and thats not accounting for the champions own kit. wu kong throws an additional 30% armor reduction in there, so hey now its 80 armor.
Their build doesn't even cost significantly more. tanks are suppose to be the hard counters to these assassins and they just cant soak their damage anymore.
And i'm not gonna beat the dead horse that is throwing conqueror into the mix jeez.
Oh, and they physically cant beat the ad assassins because they also get tank stats and defensive utility with their ludicrous penetration items.