Li Shenron
Legend
That is, IMO, exactly what skill challenges are meant to avoid. One check, if you roll bad, oh well, you lose. If you have a series of rolls, you can figure out something to help you and give you a bonus if they are not going your way. That is, IMO, the single biggest reason why 3.5's skill system sucked. Combat would be a multi-round, multi-roll affair, but all skill checks were a one and done. If you failed, sucks to be you.
This is exactly my point: if the series of roll gives you the chance to figure out something to change the course of the encounter if you think it's going badly, then the method is cool. If it doesn't, if it's only a series of the same check one after the other, then it adds nothing to the game.
But in general, I don't think we need a codified system for that. In 3e we didn't have skill challenges, but I've always seen non-combat encounters being run with series of sparse checks within roleplay or narrative descriptions. That's pretty much DM-dependent, because I have also seen social encounters be solved by a single Diplomacy check or exploration tasks being solved by a single Climb check or Search check. It all depends on the context, e.g. bartering with a seller for a lower price is totally fine as a single Diplomacy check because it's the kind of encounter where going into the details can be annoying for a lot of people rather than fun, while the discussion with your Lord M. would be disappointing if solved by one check alone, but it doesn't improve if instead of one dice you're just there rolling the same dice 7-8 times, merely counting successes and failures until the skill challenge is over. It totally depends on whether the group likes skipping over these types of encounter, while another group wants more details, and yet another group wants roleplay only. In the Lord M. case if you want it more interesting you need to make it more dynamic; in 3e we would have just mixed RP with a free series of checks, some of which were dictated by the DM and others were proactively requested by the players, there was no need for skill challenges as a rule.
Bottom line, IMO skill challenges are not so much needed as a codified rule. Instead what we really need is that adventures offer enough material to handle those non-combat encounters tactically, and good guidelines in the DMG. But not something that reads like "you need 5 successes at Diplomacy to get result A, you get B if you do 3 failures" because if that's all, that's not really different from one roll. Rather something more complex and free-form that suggests what the players can try.