Red dust definitely dropped in the Throne room last night - but not sure it was on the Large Fire Goblin. Might have been one of the other two in the room. It apparently drops elsewhere as well, because someone that was coming to keep me company and camp for red dust got some on the way in.
The Red Dust is for a druid quest for a free 10dd root necklace called the warden symble or Tunare it should be a random drop off of all the goblins in the zone
Just been in here today (....all day!) Red dust (if it looks like a little bag/pouch) has been dropping off various gobbos (though generally higher ones like infernos) round Efreeti pits/Captain room fairly regularly.