I have the regular D800 and experience the same problem shooting jewellery. I foolishy asked the same question over at DPreview... that's the last time I ask a question over there! Idiots aside, I found two workarounds, thought I've only tested one.
1) switch live view on in M mode, then switch to movie mode. Open the aperture and slow the shutter and the live view is much brighter. When focussed, switch back to regular live view (or switch it off, seeing as it's fairly useless) and shoot away, the camera will remember the Manual mode settings separately to the movie mode settings in live view.
2) shoot in A mode using one of those new-fangled pocked wizard thingamies that is specific to nikon flash. I have been told that adding one to the hotshoe sets the shutter to 1/30 so you can shoot with studio lights. All other modes in live view don't have exposure simulation. (i'm not convinced with this one, sounds a little iffy to me)
there is a firmware update coming. I have spoken to Nikon UK about this and whinged at great length. Whether they fix it or not is another question though.