Exhaust still lowers enemy AR/MR by a flat 10. Why? Doesn't it feel tacked on?

It can help you dominate early, but no one takes Exhaust for that part of the effect, so why is it still there? Doesn't it just take up part of Exhaust's power budget in poor ways?

If we want to keep that AR/MR reduction part, I think it needs to reduce those stats by a percentage so that the reduction stays relevant in late-game. If not, we could remove that part and either put more power into the slow/damage reduction components, or reduce Exhaust's cooldown as compensation.