Using elf is better for blood sacrifice. Later game you want to maximize your element (like fire). Once that is done, you want to put points in scoundrel to maximize your crit damage bonus.

To make a crit build work, in act 3 you want to start looking for gear that has + crit chance. Prior to that, put the scoundrel points in huntsman as high ground is easier to get.

Nothing else matters that much.