Nadesco, desynthesis doesn't follow the same rules as synthesis. You only need capped skill to reduce failure. It's actually not a HQ3 at all, but the lowest chance of obtaining a material. (That's how 'HQ' rank is determined after all.)
I disagree with you Karbuncle. Just because desynthing is less consistent then normal synths does not mean it is random. There are days when I break 10/10 on goblin gear and others where I hit every HQ. SE has a system in place for everything in the game... we just don't know it yet.