There must be at least X number of dice rolls, up to so many successes or failures, to the prescribed DCs. No shortcuts around that are kosher, because rolling the dice -- pretty darned precisely just that -- is how you 'earn' the experience points.
This feature of skill challenges is not very different from the fact that no matter how creative my PC's plan in the arena, I must hit the monster a certain number of times to eliminate its hit points.I don't want to be "creative" about coming up with an excuse to roll stat X some number of times. I don't want to be "creative" about rationalizing why nothing I do changes the need for so many dice rolls, or by much the consequent previously established probability of success or failure.
I want to be "creative" about about making my own plans and seeing them succeed or fail on their own merits.
One imagines that, on occassion, there will be circumstances in the arena combat in which something so unexpected happens that the monster's hit points become irrelevant. Perhaps I find a way to trick it into stepping into a sphere of annihiliation.
The same can equally be true of a skill challenge. In fact, DMG2 makes the point expressly (at page 82):
Is there a chance that a really good idea could completely trump your skill challenge? Don't fret! That's a good thing. D&D is a game about creativity and imagination. . . When you build a skill challenge, be prepared for it to head in a direction you didn't anticipate or for the party to fail utterly. That way, the game moves on regardless of what happens with the challenge.
I don't think this is very radical stuff, though.
The stuff about earning XP is more interesting. DMG 2 made a significant addition to the XP rules - one monster's XP for every 15 minutes of significant, focused roleplaying. Essentials has made a further significant addition - XP for a skill challenge are received whether the PCs succeed or fail at the challenge.
This is consistent with the notion that the main function of XP in 4e is to generate a change in PC level over time regardless of what exactly the PC's are doing in the gameworld. This in turn would fit in with the notion of levels in 4e, and particularly the half-level bump to attacks/skills/defences, that I have been articulating since the game was published, that they produce a game in which "the story of D&D unfolds" - first the PCs fight goblins, then gnolls, then trolls and ogres, then drow, then demons, then Lolth and Orcus. It's not so much about ingame power-ups (paragon paths and epic destinies represent this).
So the upshot is that circumventing the skill challenge won't cost XP - because the time spent doing other things (roleplaying, fighting, another skill challenge) will substitute for it.
Again, not everyone wants to play this sort of game. But some do.
(Oddly, then, 4e is in this respect perhaps closer to Classic Traveller than to classic D&D - the aim of play is not to accumulate the most XP for the least risk, but simply to pursue the goals of the PCs within the gameworld. Level ups help shape the changing character of that gameworld relative to the PCs - that it, at higher level they will meet more demons and fewer goblins - and also give the players new tricks to enjoy, with new powers, retraining, etc. But they don't bring the PCs closer to achieving their goals, which have to be understood in purely ingame terms.)