There is nothing to stop assassins from nearly soloing whole teams. Anything that is not a tank is dead before they can react. Even tanks, Which are supposed to directly counter absurd amounts of damage are being absolutely shit on by assassins only surviving for 3 hits.
The issue is not flat damage Its not magic pen its not armor pen. Its Lethality.
Lethality IS armor pen.
There is nothing to stop assassins from nearly soloing whole teams. Anything that is not a tank is dead before they can react. Even tanks, Which are supposed to directly counter absurd amounts of damage are being absolutely shit on by assassins only surviving for 3 hits.
The issue is not flat damage Its not magic pen its not armor pen. Its Lethality.
Hasslich alredy answered but omfg Lethality is a reworked Armor pen, the issue on this regard is they effectively gave alot more to work with by bringing in 
and 
, which the edge of night is part of the issue being a much better 
by letting you time that shield to make it highly impossible for diver junglers who use it to 'easily' secure a kill against champion who would normally be able to CC them so they are stuck under the tower.
What they did not do properly is setup Lethality to put in proper preventive measures so people can't be doing lethality builds with runes and masteries nd then grab straight into lethality items to what can easily rip over half a target's armor by the time they got 
, maybe even 80% of it depending on a few things.
This does not even help that buying a 
, at least to the best of my knowledge, will not be able to deny much of a snowball if two lethality stacking opponents can jump on you, CC you hard and secure the kill and then easily stack more lethality then you can buy the necessary items to counter them AND build your damage items as a mid laner or ADC. Much less doesn't help if the enemy team has a mix of high burst AP and lethality AD so even if you counter build against one, you'll be stuck being blown up by the other while the other can still harass damage you even thru your counter building.
[zombie-brand-facepalm]
