Just killed one, and it dropped Mythril Ore. I have yet to see Darksteel Ore, but I can tell you he does drop Mythril Ore, very rare drop though. We've killed at least over 20, and only 1 of them dropped an Ore. Of course now that I said that, I won't see another one for another 50 mobs, but ah well =P
As someone who leveled down from 72 to 71 hunting for a Moongate pass a couple weeks ago, I can absolutely positively assure you that Judai's right, these buggers are SIGHT AGGRO. ;_;