The NPC "an amorphous mass" (the unusually large black goo) in Dragon Necropolis was pulled and downed this weekend by our raid force, and when it died it did not split into more goos. There is a ZAM post on this monster from around Velious era that indicates it did used to do this. Not 100% on it, but I remember this mob having this "split" mechanic when killed.
http://everquest.allakhazam.com/db/npc.html?id=5425
2 posts from the above link (one 4/14/01 and other 2004 indicate that this occurred on this mob)