Just to clarify for those that aren't sure. This whelp can drop from ANY of the blue dragonkin around Lake Mennar in Azshara as shown here:

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You have 4 types to farm which are as follows:

More East of the lake, higher level larger elite blue dragonkin:
Draconic Magelord - Level 53-54 Elite
Blue Scalebane - Level 52-53 Elite

More West of the lake, lower level smaller elite blue dragonkin:
Blue Dragonspawn - Level 50-51 Elite
Draconic Mageweaver - Level 51-52 Elite

So basically, any of the blue dragonkin has a chance to drop the Azure Whelpling, so no need to worry that your killing the wrong one. ^^