While not a bug and it is said to be intentional, this still feels like a major problem to me. When the new expansion launched, Death Knight's core cards changed and the previous cards went into Legacy. While normally this isn't a big deal, these were the cards that acted similar to the other classes' basic set. When the other classes had their basic cards go into Legacy, they remained in your collection whether they were uncraftable, opened from a pack, or crafted with dust. However, for Death Knight, ALL of the cards were deleted from your collection and none were just made uncraftable.
This leaves most (wild) Death Knight decks unplayable unless you spend a lot of dust crafting cards that were implied to always be a part of your collection for free, like how the other classes act. The total dust of all these cards that were yoinked from our collective collections is a ridiculous 8,040 dust. This makes it completely unfeasible to recraft even the cards needed for some singular decks, much less the whole collection after having already spent dust on the new expansion.
Let me remind you that all the other classes have at least *some* free uncraftable cards in Legacy. Demon Hunter in particular, the only other class added post-launch, has almost *all* of the cards be uncraftable with the exception of a single legendary called "Kor'vas Bloodthorn". All of this had heavily implied that Death Knight would function the same way, because why wouldn't it? The only reason for Death Knight's Legacy cards to *all* be taken from the collection is for Blizzard's growing greed.
(I have “sad face” in parenthesis since it won’t let me have emoticons in the title)