I honestly don’t remember because it has been too long (over a year) since I last played on retail, but recent research suggested that a red ! is used to indicate that a creature starts a quest upon being killed. Is it possible that DIALOG_STATUS_UNK is used for this purpose? Having run 10 characters through Uldum, I remember 2 beasts (hyenas and vultures) giving a quest when the first one was killed in the zone.
hyenas (entry 45202): http://www.wowhead.com/quest=27187
vultures (entry 47202): http://www.wowhead.com/quest=27940
The red ! may not have actually shown on them, thus my asking for feedback.
A 3rd quest seems to follow the same design, in Vashj’ir.
eels (entry 41002): http://www.wowhead.com/quest=27729