1) HDR mode is available if you "must have" that DR
This is simply wrong, if something moves (and in nature, most things do) hdr won't work, you can blend a hdr with some non-hdr parts but this is a pita.
Also, a high DR sensor is HDR done with one shot.
Not when you are talking about the difference between 12 and 14 stops.
yea exactly. moreover, and I hope this doesnt degenerate into another set of awning pictures, because most of us get that the extra couple of stops is not a bad thing. When certain conditions prevail, namely:
* you must shoot at low ISO, where the D800 DR advantage would be available (which it is not, at high ISO)
* the scene is noteworthy
* you must capture the shot with one exposure
* the required shutter speeds are too slow, or the requried resolution precludes handheld IS
* the scene contains detail that is important to the meaning and effectiveness of the photo, that is beyond the DR capability of your sensor
...when all of the above converge, having the extra two stops of DR in-camera capabilty is a benefit for sure. This may apply to some 'togs all the time and it may rarely, or never, apply to others. however, it is also worth pointing out that when the above situations all come together, or the photographer makes them come together to get the photo, that a tripod and/or other suitable support is not out of the question! in which case one can indeed blend exposures and capture a great deal more DR than a D800 single frame is capable of.
I am not trying to sell popcorn here, believe me, or bring out the awning wars again. I'm just pointing out that one really needs to determine the extent to which the DR advantage is really important to the situation.