Please, DO NOT NERF EXHAUST
Here me out. I know a lot of mid/top laners have been picking up exhaust more then usual lately, and that it does have its strengths, but exhaust has been untouched since the beginning of time, and it has always been perfectly balanced. There are some champions who rely on this spell to keep from getting 1 shot under riot's lego turrets at lvl 5 by lethality riven, not to mention
COMPLETELY REMOVES EXHAUST and has 210 second cooldown, along with being useful in other situations as well. if 17/3/10 irelia didn't finish your team off because of exhaust then she has 210 seconds to wreck face in every other team fight.
tl;dr
- exhaust is perfectly fine where it stands
- it can be countered

- reliable way to keep lane bully champs from destroying you with no counterplay
And for f*ck sakes if you do nerf it which you probably will just raise the cooldown a little bit instead of adding some "scales with level" bullshit or removing a debuff its actually useful for