I wish ICC worked the way that the 5-mans work.
Here, let me explain it a bit better.
Each wing is a separate raid instance but in order to progress to a further wing you have to defeat a prior wing.
So you go through the first wing up past DBS. Easy. Now you have access to the next 3 wings, then you have the LK himself.
The lockout is refreshed every week so you can't just skip right to the LK after having gotten there once.
Now the reason I want this system is for one very big pro.
There are a lot of pugs that can make it past the first wing but then everything falls apart, so you say that you'll come back later to try the other wings, but when that time comes around you end up seeing things like "LF1M Healer, on Festergut" and that stinks. No healer wants to get saved to the raid when 1/4 of the bosses are already down and the group has a pretty high chance of failing.
Not to mention let's say your group does the first wing, but everyone bails and you can't get into any other wing. So here you are stuck on that lockout even if you personally could go further.
So yeah, for larger dungeons, as in not ToC, I'd like to see a more sectioned raid with separate lockouts. I think it would keep up the ability to pug and make the game more fun for a lot of people. As well as make the instances slightly less tedious and help raid groups where you end up with those times when one person you really need just can't make it.