I cannot understand any arguement that prevents release of new content. If you are not good enough to clear the content in the alotted time, then you need to either step up your game, or get past the fact that you are not a super duper awesome player.
And, there is absolutely nothing wrong with working on previous tier content when the new tier is released. If you really are competitive, then you have cleared the necessary content. If you are prentending to be competitive (when you really aren't), then you need to get over yourself.