You have to remember a few things. When you queue in that instance most of the people are wearing gear multiple ilvls higher then that dungeon. So if it were scaled around ilvl 70 then someone who is 80 queuen might be in 490ilvl gear.

The dungeon is supposed to auto adjust that gear and abilities to ilvl 70 but that is not always a smooth process so you go in a nuke the instance especially with a very geared tank and healer. Any healer in gear that is actually lvl 41 for Stone Vigil would not be able to keep up with the healing demand.

There is also hard modes for Stone Vigil that I never see anyone chain pull.