You used to be able to build armor on any champion if behind to help you catch up but not anymore. Armor has to be the most worthless stat in the game at the moment.
I don't think AD is the problem, I think the problem is that too many AD champions have abilities/items/skills that completely bypass armor.
at level 18 has the lowest base armor at 68 outside of thresh and mini gnar. With 
, she has 113.
With , you have 39% damage reduction against 
without , you have about 15% damage reduction against
Without any health items, has 1860 health at level 18. Let's say that the enemy does 3000 damage before reduction.
With , they deal 1830 damage. Congrats, you lived.
without , they deal 2550 damage. Dang, you died.
That's why you build armor.
I think if you build armor on a champion they should actually be wearing armor and become bulkier.
I have one loss as Nasus this year…I build at least 2 armor items: 
and 
. Possibly more, depending on the scenario.
Lethality isn't as OP as you think it is.
