The five Oath cards from the Exodus expansion are very powerful enchantments, and many of them lends themselves to decks. Oath of Druids and Oath of Ghouls both power dominant Extended decks, and Oath of Scholars was tried in blue weenie decks as a source of card advantage. Even Oath of Lieges has seen play in weird creations featuring Stasis and Squandered Resources.
But what about the red one? Oath of Mages? The red Oath was a victim of cycle symmetry. It was initially designed to do one damage per turn to the person with the least life, not the most. Red decks tend to do better when the opponent is down on life, not up, and this card was a good fit. But it was changed to fit the other Oath templates, where the player with "less" benefited.