The back of the box says that this game is based on AD&D 3E rules. While the game may take some plot elements and locations from D&D, the actual combat rules have nothing to do with the actual 3E rules. This makes for shaky balance at best.
The game can be challenging, but more or less its a "wait for health/mana regen, then go tackle the next wave of monsters". Don't get me wrong, fighting is entertaining, its just the waiting for your health/mana to regen that bothers me.
I played through hard as a solo sorceress and had little difficulty defeating my foes, probably because I was a sorceress wearing chainmail with no casting penalty.
I really wish when games claimed they were based on a ruleset they truly stuck to that ruleset....