This mob does infact drop Igneous Rock of Doomfire, for the Rogue 1.5
We cleared out the area on 05/09/06 trying to get the rock from the Magus mobs, and decided to try these even though it wasn't listed. Got down to three mobs left and it dropped :)
Max hit 188 on a tank with 2315ac.
Resisted magic debuffs, did not resist magic nuke often (once or twice out of a ton of mobs).
Doesn't run.