Cool shot!.

It looks like the two spires have been cut off at the render tile borders. I bet the 'finished rendering' 3D preview image doesn't look like this, with both spires exactly as tall as each other and cut-off perfectly horizontally, does it?
I think increasing displacement tolerance is supposed to help that but I've never seen any improvements when using it for this reason(I've tried to correct these issues before by this setting and had no luck)...
You might try crop-rendering the central two spires with only *one render thread* so as to not cut off the spires at the AA bucket borders(that's where you'll notice the cutoffs are happening).
I like the cave-painting style noises on the foreground!