No, this is not a bug.
I'm Gloria, level 30 Blademage.
Enemy is a lousy level 17 hero Christian, can't remember his hero class. But my attack was pretty close to his defense. A Blademage is a pretty good attacker, and if I remember correctly I had around 15-18 attack.
This is the opening scene in a fight. Round 1, Medusas go first as always. He hadn't cast Stone Skin or anything. And my 43 Medusa Sorceresses can't even kill 1 Abbot!
I have once written in praise of the Blademage. But that was when fighting against neutrals. Against a real hero... (I won this by blasting Christian's army with spells.)