WoWDB

This guy is a tough find. Server resets may be your best bet, however, I have consistently seen this as an exactly 24 hour respawn. Tested this by timing a server restart: Server restarted at 12:08 on Tuesday, went to the Ice Crown area where these spawn at 12:08 on Wednesday and a ton pooped up. My best guess is try to find them on a server restart. If you can't but know the time the server did restart you can try the next couple of days to find them.