The way I see it is, I have 6 skills to my choice, some single target, some aoe, others can be used to escape or be used as crowd control. Well, maybe I'm wrong but I feel like Blizzard wants us to swap out our skills to adapt to game play we'll encounter. For example, I'm heavy on single target skills; great for boss fights possibly, but maybe I am fighting huge hordes of zombies before then and I'd want AOE skills, I can do that. I don't think there is a cookie cutter build for every class, I think blizzard wants us to swap our skills to adjust to the situations we'll be facing.
Another great thing about this is, I'm playing with three of my friends, two of us are Barbs, if we both play the same wouldn't that make us weaker? If we swapped out skills to compliment each other we would be stronger as well.
Tell me what you guys think!