Even in full armor there are always parts that wont be completely covered. And going by the Adventure game I played this morning in which I was melted by two Firebirds while wearing full netherbark under my other armor it probably wont guarantee survival. If you are thinking about using it for Military dwarves who will also be using shields, then go for it. Since they will be able to block any dragonfire breath attacks if they are skilled enough, shield material shouldn't matter either. I had put my adventurers shield away a few minutes before, and then forgot to re-equip it when I was jumped. Melting to death is not the most heroic death...