It's a pretty nice image and a good choice to go B&W, but there are a few things you could do to improve this.
Firstly, from a shooting perspective, you should try to be more aware of the horizon - it should be level. Yours is getting on for 2 degrees off, by my quick estimate!
The other thing that you benefit from is learning about hyperfocal focussing which would help you greatly with depth of field and image sharpness - you'll have to google it as I don't have time to get into the nitty-gritty, I'm afraid.
It's perhaps a bit daunting at first, but is, in fact, a reasonably straightforward technique and especially useful at w/a focal lengths.
Secondly, there's a great deal you can do in post processing to lift this image to where it should be.
First off, fix the horizon using the "measure" tool in photoshop followed by rotate image "arbitrary". You will have to crop the image consequently But using a D800 you can afford to lose a couple of million pixels without too much harm.
Next off, I would work on the contrast which, in my opinion, is what is really lacking here.
Try just putting a curves layer above your image layer without adjusting it, but set its blend mode to "soft light." I think you will be surprised at how improvement there is.
Personally I would go slightly further with two additional curves layers (for foreground and sky - normal blend mode on each) on which I would adjust the curve to improve to tonal separation to my taste and the limit the effect by using a gradient fill on their respective layer masks....(I may have lost you by now! ).
Curves layers and layer masks are very powerful tools - do some research. It will benefit you greatly.
Lastly (after resizing for epz) I would use some careful sharpening to tighten it all up prior to uploading.
Cheers - hope this is of some help