After getting mad after some stole this mob after I had killed it half way. I have never seen a mob drop red while you are fighting it.<self edited rant>..
here is the sequence of spawn over 12.5 minutes
Bronze Quadav
Silver Quadav
Garnet Quadav
Zircon Quadav/Zo'Khu Blackcloud
Zo'Khu Blackcloud spawns every 4 to 8 cycles.
UPDATE
ok there isn't a sequence. just each mobs spawns 12.5 minutes after killed. so 12.5 mins after Zircon quadav is killed Zircon Quadav/Zo'Khu Blackcloud will spawn. every 4-8 cycles
Edited, Fri Jun 18 18:24:05 2004