For my own preferences, I wouldn't want the message code-forced on every raid mob. I like to pick and choose, so demonstar's db flag is a good idea.
EDIT:
The options would be left wide open for all npc's with a little sql.
UPDATE npc_types SET aggromessage = 1 WHERE raid_target = 1;
or getting a little more picky:
UPDATE npc_types SET aggromessage = 1 WHERE raid_target = 1 AND hp > 500000;
or sending out a message when someone engages the quillmane:
UPDATE npc_types SET aggromessage = 1 WHERE id = 14139;
Personally, I would love to see it spit out a we and mm server-wide message for all npctypes flagged.