When you go to the leaderboard, most of the columns are straight-forward, like number of kills, gold collected and difficulty. It's the score column I need to know more about. How is it calculated?
Score = gold earned + enemies killed (on that character). It is a widely disliked system, due to cheaters/hackers. But is it really that different on any leaderboard?
Note that in terms of leaderboard, there is no benefit to playing hardcore, nor is it directly beneficial to play at higher difficulty (although it may produce more enemies to kill).
Some speculate that Runic is "phoning it in" because they are a small studio and leaderboard support is a Microsoft mandated requirement.