Alright, so I've looked at the scene you provided...
First of all, you do not override gamma settings on normal and displacement maps. You should always set it to "use image default gamma" to use the gamma settings they were created with and since you used 8bit jpeg with 2.2 even "system default" would work.
Another thing is that to get tangent normal somehow look alive with corona you have to use higher bump values(i used 10 in this image)
However some shading issue appears to cause that noise on the sphere with normal map and it doesn't go away... I tried playing with max shading normal difference but that makes the whole normal mapping fade away.