Heavensward Art (Potential Spoilers)

[Nalien]

Are you entirely sure the concept art you just linked actually supports your argument? I actually see two eyes on that dragon. The right eye is a little obscured by the scar but turn the picture on its side and it's much clearer. If you still can't see it drop a yellow colour filter on it as he has two very distinct yellow eyes.

I see two very distinct scars, but not two eyes. Just looking at the angle I don't think it would even be possible to see his right eye. Meanwhile we have the actual in game model clearly displaying a missing eye, not to mention everything else I said. Fluffy McWhite Feathery Dragon really doesn't seem like Nidhogg; No rage, doesn't match the Drachen Armor, etc. Why is he prominent? Because he is the Celestial Dragon we'll actually communicate with? It makes sense that they'd give us a Dragon for that exact purpose, given Nidhogg has been on a 1,000 year hissy fit over his eye.

Something to remember: almost everything we know about the Dravanians comes from Ishgard. Given that they're mortal enemies of the dragons (and fallible mortals to boot) I'd be wary of taking everything they tell us as definite fact. At this point the only detail I'm willing to trust them on is that they took Nidhogg's eye, since they actually have it still and all. I'm more comfortable saying the white dragon is Nidhogg based on the obvious missing eye than I am saying he's not because he's the wrong colour.

So you're going to take promotional art over the actual ingame model we saw in the Benchmark and say the Benchmark Dragon isn't missing an eye? How many times has promotional (yes, not even concept) art shown us things which clearly aren't in game or are drastically different? Pretty much every event, no?

All the white Dragon has is a missing eye. That's it.
The Benchmark Dragon has a missing eye. The Benchmark Dragon has a very obvious aura of rage, and we're told frequently that Nidhogg is seething with rage. Think that's a lie? What, so Estinien didn't get overcome with Nidhoggs rage and almost lose himself? Guess that fight never happened? The Benchmark Dragon also has multiple scars, while the white Dragon doesn't seem to have any. Which one seems like his been in a 1,000 year war with Ishgard given that? We know Alberic managed to wound him, I imagine plenty of Azure Dragoons did over 1,000 years. The Benchmark Dragon also matches the Drachen Armor more closely.

Pretty much every description we have of Nidhogg matches the Benchmark Dragon, not the white one. You can claim Ishgard is lying about all that if you like, I'll admit it is a possibility (or rather it would be a plot twist that will catch even most NPCs), but that doesn't definitively make Whitey-McFeather-Face Nidhogg when both are clearly missing an eye. All we can conclude here is that there are two Celestial Dragons missing an eye when we previously thought there was only one. Like I said earlier, that's not really surprising since Nidhoggs Eye has granted Ishgard some degree of power, makes sense these Dragons would have their eyes sought after.

If that still doesn't convince you then take a look at the concept art of all seven of Midgardsormr's sons. That blue dragon is the one featured bottom-middle in the image (his horns protrude forwards in a very unique way) and you clearly see his right eye.

This is perhaps true, but again, promotional art often has mistakes, though perhaps more importantly, did you check the white Dragons eye? In the promotional piece with all of them, you can see whitey's left eye and blues right eye. In the individual pieces, well I maintain that you can't even see blues right side enough to make out an eye, but whitey? He is missing his left eye...

Again, it's a promotional piece (not concept) and they often have mistakes in, or things are too small for us to clearly make out. Whitey probably is missing an eye in game as well, but we have the ingame model of the Dragon thought to be Nidhogg thanks to the Benchmark, on top of that he actually fits every description of Nidhogg we've been given. This is fairly cut and dry as far as I'm concerned...