Here I would pick Deathspeaker. It works well with The Lich King and is a decent standalone card. I would say it is closely followed by Scarlet Crusader, which is an excellent 3-drop. Mistress of Mixtures, though a powerful 1-drop and a source of healing, does not beat the other two cards.
2. Scarlet Crusader
3. Mistress of Mixtures