Update 18.0a fixes a problem which prevented some high scores from being uploaded to Steam. The bug affected most of the games with very good scores, and thus the leaderboards looked as if mostly nobody has ever beaten the second boss. View your local scores ("View achievements and the Hall of Fame" in the menu) to send them to Steam. Unfortunately, your local scores will not be uploaded to the "no potions of life" leaderboards if you later used a Potion of Life in the given game.
Also share your game logs or strategies on the forum! http://steamcommunity.com/app/432380/discussions/0/371918937262956260/