Go play Diablo 2 up till Blood Raven in Act 1 Normal and tell me how hard it is.
Skeleton King is 1/3 of the way through Act 1 Normal. There are 3 difficulties beyond that. You're not the brightest bulb on the tree. That's for sure.
As for mana. There are energy generating skills, and energy hog skills. When you're using literally zero mana, it's cause you're using an energy generating skill.
Maybe you should have done some research before coming on here and showing your ignorance?
Anyways.
See you at launch. I HIGHLY doubt you cancelled cause easy mode was easy. lol