I fixed the displacement warping issue by taking the file into Photoshop and softening the contrast around the warped area, but leaving the rest as it was. This leaves the rest of the arm with the desired amount of detail from the displacement map, while giving the previously-warped section a reduced effect.

However, saving the .exr out from Photoshop heavily reduced the contrast of the map, so it took a bit of time to get all of the settings correct to give the arm a look that is consistent with the rest of the model.

I've got all of my displacement maps in Maya and applied to my model. Each of the materials had to be tweaked here and there to give the Giant a consistent look although I'm going to need to make further changes to his left upper arm (the right upper arm from this renders view) as there's some noticeable stretching if the settings are too high. I'll be experimenting with a few ideas I have to fix this issue and post what does/doesn't work.

I've been working a lot to create a good medium between render quality and render time to give myself something more manageable, and I've been able to lower the render time down from 3:04 to 0:38 with no real noticeable drops in quality.

The lighting I have set up currently in my scene is pretty harsh so I can clearly see the effects of my displacement maps as I apply and edit them.

I doubt this process will take too much longer and then I can finally get onto rigging!