I don't understand the overreaction of some here. Lowering by 0.2 (the maximum DE can nerf a riven) is negligible in most cases. Remember, 99% of the enemies in this game die with a single spin melee attack or a bullet to the head of any good weapon without the need of a riven.
The only weapons that notably get nerfed by such small changes would be shotgun type weapons where you have a riven that barely lets you get past the 100% SC. Example, if you have a Kohm riven with 120-123% SC and it gets nerfed to under 120%. In any other scenario, your 1 shot weapon will still 1 shot.
If you want to complain about something, complain that there is no challenge in this game where our rivens would actually be used.