Missing Cards in Twist?

I was pretty excited to play the "journey through Hearthstone" Twist arrangement for this month, but I seem to be missing quite a few Legacy cards. Loot Hoarder, Spellbreaker, Stranglethorn Tiger to name a few. I can see them in my general collection, but they are not available when building my Twist deck. To add insult to injury, I faced an opponent who played 2 out of those 3. Anyone have this experience, and know what's going on?