Scourged Whelpling

Scourged Whelpling |
Battle Pet |
Pet Battle: Icecrown
This pet is not tradeable.
“Kel'Thuzad once nursed a plague-infected whelp to adulthood, feeding it only the finest liquefied remains.”
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.
Instead of levelling a dk, if you have a friend on a low-populated realm he can invite your toon there, so you can cross-realm and capture the pet without much competition. Also keep in mind that if you are flying over the area using a taxi-service, you will see the green paws on your map but if you fly back on your mount, most of the times you will be disappointed. It's worth checking nonetheless :)
The easiest way to catch one is to invest 1 hour to level a DK on a really low populated RP server, since the pets are account bound. Choose a PVE server, so you cannot be attacked by a higher level player while having a pet fight. Create a DK, get through the starting quest until you get to OG or SW, then simply take the flight point next to the taming area.
With this toon farming other rare pets is also easy as hell since the servers are empty like the Silithid Hatchling and Minfernal.
Get yourself a map addon like SexyMap (http://www.curse.com/addons/wow/sexymap) where you can maximize the size of the minimap so you don't have overlapping pet trackers.