I've done the Zul'Gurub quests, and I want my raid back.
First of all, the quests that involve Zul'Gurub would have worked just as well in an instance as they did on the world map. You never walk in through the front door, you get teleported in and do strange little tasks.
Second, they took maybe 10 minutes in total, all of them put together.
I can't entirely rule out the possibility that we will be sent back there at higher level, but if you are so far Wowhead knows nothing about it.
I realize that no one even set foot in Zul'Gurub aside from a few dedicated mount collectors, but what they put in to justify removing it doesn't have a whole lot of value either. My position is clear skewed by the fact that I was one of those people farming for a mount, but comparing what was given up to what was put in its place - and the development lost plus the development that was put into the new stuff - it seems like a bad trade.