Destiny is coming out very soon, and that means future players are probably thinking about what the endgame will be like. The latest update on the official site shares some more details about how raids will work in both Normal and Hard modes and elaborates on the differences between difficulties. In short, Normal mode is meant to be far easier and allow for more diverse clearing strategies; Hard mode demands coordination and execution.
Opening raids for the first time is meant to be challenging; the devs shared an anecdote about players taking 45 minutes just to get in the front door. The developers are confident that players will be able to tackle raids more quickly once the raids are better known. There's also discussion about the weekly lockout, which will save your progress as you move through the raids. Take a look at the official update for more details.