Just to point out that this is how I have always interpreted the 4e skill challenge DC table. That the level of the skill challenge in question is based not on the PCs level, but on the level of what the are attempting to do. Trying to ambush Orcus in his lair is always going to have DCs associated with a high epic skill challenge, no matter whether the PCs are low paragon or high epic.
It's explicitly not that, though. Otherwise there would not have been 3 PC levels all with the same DCs, in the original versions of the table. My own table is better because (a) I can hold it in my head and (b) every particular DC number appears in it once, not a redundant 3 times. Each DC number has a particular in-game-world meaning associated with it, eg a DC 24 is a slightly easier than usual moderate-Paragon task, nothing else.