In Regards to lethality and champions.

Simple really before you start nerfing champions into the ground who abuse lethality (see quinn and MF) and leave some of them alone ( see pantheon varus and jhin) inevitably nerfing lethality when you realize that you can continously nerf champions who use lethality because their is too many the champions you hit with the nerf bat the first time around are going to be in an even worse spot than they were before (again see MF and quinn) her kit was perfectly fine if you built her as a marksman now her and mf are being directly punished for lethality when yes quinn may one shot people with lethality but she is so squishy that she is only good for one target. Meanwhile jhin has two slows and a stun and very long range safe poke. varus has long range poke combined with percentage health damage if he gets collapsed upon he also has a stun that roots to other people and a slow to help him escape further. meanwhile quinn has a vault that provides a slight displacement and slow hell at least miss fortune has an aoe slow and movespeed up.

Long in short of it, stop messing with champions when they are not the actual problem and its lethality, you need to realize this.