Alright, I found a few things that might help.
One issue is that the camera is so far away it makes it hard to see the normal mapping.
This is a close up shot of the handle:
I had to substitute in my own Diffuse/Normal maps for the leather, so they may be different from yours.
Now look at the same image from further away:
You can see that the normal mapping is still there, but it's harder to see.
Another thing I noticed:
Turning up the Fresnel option in the ray tracing helps. Fresnel is how much the non-reflective bits are blended with the reflective bits, which seem to not show the normal mapping very well. More blending means more parts of the handle are bumpy.
Also, try playing around with your OSA settings, you can change the filter method and size. A larger filter size seems to retain more detail on the model at the cost of slightly jagged edges, I got good results using the 'CatRom' filter and a filter size of 1.25
[EDIT]
Another thing I just thought of: You could try making the size of your normal/diffuse map bigger. Obviously super small bumps are going to be very subtle from further away, just like in real life. So if you make your image larger, the bumps will be bigger and more visible.
Check it out, I brought scaled my image to 0.75 instead of 1.
(In blender smaller numbers are bigger for scaling).
I've been using a normal mapping setting of 3 for all of these shots.
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