<p>It does not work. The reduction of damage is about the raw solidity of his skin above his Immunity that could reduce an A-Rank attack to D. But Ex-rank are beyond powers. </p><p>
</p><p>In RPG terms, a D-rank Noble Phantasm deal 10-20 damage, a B rank deal 30-40 damage, and a A-rank deal 50 damage and more. The ability of his skin is to reduce those damage by 40, more or less, which reduce greatly a A-rank at a D-rank level. however, Ea for example would deal an equivalent of 4000 damage... (I am using the Visual Novel value here).  </p>

<p>E Rank not D rank, so 10 or less damage, but other than that it's fine. </p>

<p>I believe that, regardless of rank, it depends on the manner in which he is attacked. If it's an attack of phyiscal nature, or magical that hits physically (Fireball, stone slab, or blade of energy), it is first reduced in power by the armor, and even if it punctures the armor, the armor still resists the damage, causing a rank down in damage. However, if it's not physically striking or damaging (Curses, command seals, or the like) then it won't really be affected by Armor of Fafnir. And of course there are those attacks that are either A. So Powerful they override his defenses, or B. Just shred through it like butter. Ea/Enuma Elish and Excalibur are good examples. But it's defenses are pretty much why Sieg survived Clarent Blood Arthur. Without it's resilience, he'd have died during that attack because, like Godhand, it wouldn't lessen the damage taken. </p>

<p>Technically he would reduce Excalibur, as he did for Clarent. The major (the ++) need conditions. And unlike god hand, it's not only an immunity but a protection. So if Hera take full damage of Exca, it's not his case. </p>