It might not be a bug, as far as I know some classes get a boost in some of the different card types.
BM/Barb/Seeker get 140% from Longevity / 80% from Durability
Archer gets 80% Longevity / 120% Durability
Sin gets 80% Longevity / 120% Durability / 75% Battle / 75% Destroyer
Cleric/Mystic/Veno/Wiz/Psychic get 40% Longevity / 140% Durability