The way the new armor pen works, If you have armor pen runes and 2 armor pen items, basically all of darius's attack/skills will do true damage to everyone except tanks.

%armor pen maxes out at 75% but new last whisper is "ignore armor" not armor pen, so darius practically ignores 400 armor on everyone.
Here is how

The Black CleaverCost: 3000 (1188)
+250 Health
+50 Attack Damage
+10% Cooldown Reduction
+15 Armor Penetration

Passive: Dealing physical damage to an enemy champion reduces their Armor by 7.5% for 4 seconds. This effect stacks up to 4 times.

7.5X4= 30%+15 flat penetration

Last WhisperCost: 2135 (860)
+40 Attack Damage

UNIQUE Passive: You ignore 35% of your opponent's armor.


so 25% armor pen (passive E) + 8% from masteries 30% armor reduction from Black clever + 35% ignoring opponent's armor
That means you penetrate 33%, reduce 30% and ignore 35% which is 98% of armor negated. =\

LETS SAY you have 90% armor pen/reduction/ignore(total) instead of 98%
STILL
you have flat 15 from Black clever and with runes you have about 25 that is about 40 armor pen (flat)

IF you have 400 armor, take off 90% which will leave you with 40 armor, and with 40 flat, you have 0.

so darius does true damage to you even if you have 400 armor =\

Fix darius soon!

Okay, let's do some math here.

Masteries give 8% + 5 Armor Pen
Runes give up to 22 Armor Pen if you take full armor pen marks and quints
Last Whisper gives 35%
Darius's e gives 25%

So in total, that's 63% + 42 armor penetration.

So yeah, that's a lot. But armor's not really the best thing to build against Darius anyway because he already has magic damage from his passive and true damage from his ult. If you want to counter Darius, you build health instead. So he's not OP, you just need to know how to counter him.

Last whisper is still armor pen, they just changed the wording for some reason. It still works the same as before.

Black Cleaver doesn't work the same way as armor pen though. It actually reduces the opponent's armor, so it applies before any of your armor pen. So a Last Whisper would be less effective if you also had a Black Cleaver.

so if you had 100 armor, reducing 30, so last whisper would work on 70 armor? that makes alot more sense but even with darius's E passive, and the way flat and % armor pen work, he would still be able to ignore about 130+ armor. Thats just too much specially with his W

Yeah, you're right. And I do hope they nerf Darius's ult at least, only because it turns him into a killsteal champ. But Darius's kit is designed around bypassing armor, that's just how he works as a champ, so the way to counter him is to build health. Darius could hard counter a Malphite, but I would not pick Darius against a Singed in a million years.