The Warlords of Draenor Digital Deluxe was removed without warning from the Blizzard store a few months ago, making the bonus items unavailable for those still looking to collect them.
However, Blizzard has brought back those items for a limited time sale. [source]
Bonus Item Bundle
special bundle for $20 (USD).
This bundle includes the Dread Hatchling pet as well as other bonus items for other Blizzard game titles. These collectibles only come with the Digital Deluxe or Collector's Edition of WoD.
To be eligible to purchase the Digital Deluxe bonus items bundle you must have an active WoW subscription and a WoD Standard Edition license attached to your account.
The bonus item sale will end prior to the Legion pre-patch (date currently unknown), so better not delay. This could be your last chance to collect the Dread Hatchling pet!
Special Limited Time Sale: WoD Digital Deluxe Bonus Items
December 18, 2015