In a RAW SC, the objective is to maximize the number of times your best skills are rolled and minimize the number of times that anything less than the party's best skills are rolled. Because the counter-arguments are directed at potentially unskilled PCs, they provide a reason for the 2nd and 3rd best character to make persuasion attempts.
I'm not at all sure why it would matter which side makes checks. I'm just saying, the principle with SCs is just generally that PCs do all the dice tossing. It is merely a simplification which streamlines play and keeps the action focused on what the PCs are doing. An NPC making a counter-argument is simply an obstacle. Whichever PC it might be directed at (if it is directed at a specific one even) will be able to make a check, possibly even choosing a specific counter-argument/tactic (IE using a favorable skill).
I'm a little confused by your response. In my scenario the PCs were always the ones rolling the checks. The purpose of the counter-argument is that it continues the persuasion in a way that is unfavorable to the PCs. The NPC can direct it to a particular character (usually not the one with the best score) and, because it covers a particular topic, it limits the evidence / touch points that the PCs can bring to bear.
I also find that it makes the SC more exciting (because the PCs want to win before the next counter-argument) and creates a nice ebb-and-flow to the conversation. "I see you point. What about...?"
More importantly, under this system, the primary emphasis of the players is on having their characters martial the evidence in the game world to make good arguments. This is critical because it means the players are thinking about the in-game situation at least as much as the out-of-game mechanics. Also, because the persuasion mechanics provide a standard use for skills, it forces the scenario designer to concentrate on "what evidence is relevant" and "what does this NPC care about" instead of "what skills are applicable".
Again, I think that this is pretty much normal for SCs unless the DM is particularly uncreative. Naturally you DO want to allow players some leeway in what skills to use, but the SC system was NEVER intended to be "pick your best skill and make up a reason it would apply."
Well, I suppose it's normal for
good skill challenges, but most of the published skill challenges include nothing but a list of skills and the plausible reasons PCs might use to bring them to bear. It is quite unusual for a published skill challenge to allow for the players to think about the actual in-game situation as something can be solved on its own terms. Typically, the in-game situation is nothing more than a context that players use to provide excuses for using their best skills.
Oh, I think it is fine to build up a repertoire of 'tricks and devices' to use where you can say "OK, someone is arguing with the PCs, you can approach that like THIS" etc. That's fine. I am just of the mindset that in general the mechanics can be at most minor variations on the straight up base SC. There certainly can be ones that are very specific to a certain situation where you create a somewhat different mini-game, like the Suderhome example in DMG2. You just run the risk sometimes of those types of challenges suddenly blowing right out of your set of assumptions (like lets say the PCs decided to burn down the whole town, your highly customized mini-game probably won't handle that well but a vanilla SC is more likely to stay applicable because it is so generic in rules structure).
I agree that the non-combat mini-games (as it were) should be mechanically light and use the same underlying constructs. As an initial starting point, I think of each of them as being "a skill challenge, but with a twist".
For example, PirateCat's chase mechanic involves the characters keeping a running total of their successes to represent the distance between the characters. In other words, if I'm at 105 and I get a 22 on my check, I advance to 127. If that equals the target's distance, I catch up. If the target opens up a sufficient distance, he gets away.
For another example, Mike Mearls provided a framework for the alert status of the Hill Giant Holdfast. An infiltration game (and many dungeons are appropriate for an infiltration game), consists of doing things that might affect the alert status mechanic. Either one or two stealthy PCs are trying to sneak in and out before the alarm goes off, or the PCs as a whole are trying to make progress in the dungeon before the residents rally to its defense.
Ideally, these structures should feel something like the in-game challenge and reflect the type of tension that is appropriate for that type of scenario. Also, a set of standard mechanics allows GMs to focus on what makes this particular persuasion, chase or infiltration different rather than how to design that type of scenario from whole cloth.
Of course, the game also needs a free-form skill challenge mechanic. (Creating mechanics for every possible scenario is, indeed, a fool's errand.) However, I would guess that at least three out of four non-combat encounters fall into 5-10 common types. Let's have some simple standard mechanics for those.
I mean, most versions of D&D have rules for weather and overland travel speed. Why aren't there rules for forging past natural obstacles? It's a staple of the genre, but any DM who wants to have his PCs brave Caradhras needs to create a fresh set of mechanics from scratch.
-KS