Riot almost never nerfs anything in this arms race.
AD DPS > Armor > AD Burst > AD DPS
Yet the overlap between them in different class designs means that it just keeps cycling through buffs which just end up circling back around to buff the class which had previously been the cause of another buff.
E.g. Marksmen are too strong, so we are going to buff their counter AD burst champions... AD burst champions are too strong, so we buffed their counter tanks... Tanks are too strong so we're going to buff their counter Marksmen!... ... ... ... 4 years later, it's 2018
Then let the cycle continue.