In the Cypher system approach to skills, skills do not represent a specific set of player capabilities. Instead, the skills assist in all relevant cases -- with relevance defined by the group and the context. If a character has a skill in bluffing, all tasks that involve bluffing become a little easier. There is not a specific set of moves or actions linked to the specific skill. Instead, the player needs to assert that her skill at bluffing will help her in a specific context. The skill will clearly apply in a situation where the character is pretending to have an asset that she does not actually have (possibly as part of a hostage stand-off - or simply poker). Does it apply to all situations where a players is pretending to have different credentials than they have? Does it apply when a player wants to exaggerate his strength to intimidate an opponent?
This approach to skills has become increasingly popular. In a previous post, I noted the similarity between the Cypher System approach to skills and 13th Age backgrounds. One can see similar parallels with Fate System aspects. In each case, the game includes a great deal of ambiguity and flexibility to allow players to participate actively in the game and its narrative.
The result is a system in which the influence of any individual skill can range in its coverage. Some skills may have relatively narrow ranges of application. Some question whether the result is an unbalanced skill system.
Is Balance a Problem for Narrative Skill Systems?
It is fair to ask whether having balance across skills is even an issue. The Cypher System does not emphasize traditional sorts of balance across players. In some systems, it is important for each character to have a similar power level. In these systems, it would be a major problem if one character was able to deal out a great deal more damage than the others.
The narrative skills system may have similar problems. If a skill in bluff can cover all of the situations in which intimidation would be useful, why would you ever choose intimidation? Does it render character creation options that include intimidate "less powerful" than options that include bluff.
In the playtest for The Strange, my players ran into this problem several times. Even focusing on the recommended skills (while lacking an exhaustive list, the game does provide several examples and recommendations), imbalances became obvious. Training in "all positive social interaction" is a fairly broad ability. Boundaries between "persuasion" and "bluff" are blurry. This frustrated some of my more rules-oriented players.
The clearest example is in the lore/knowledge skills. One could be skilled "medicine" or "biology." The biologist in my group was fairly adamant that medicine is a subset of biology. This raised a question of whether anyone would ever choose medicine over biology. Similarly, my would one focus on "high energy physics" or "astronomy" rather than "physics?" Could one simply be skilled in "science?"
There are some other potential problems of balance unrelated to one skills subsuming another. The primary problem is the differential utility of some skills. It seems clear that MCG saw this problem for weapon and attack skills. Putting some skills off-limits or behind gates indicates a sense that these skills are more important than others (and should be taken at the first opportunity). I have seen few people pass up "perception" or "speed defense" for similar reasons. In combat oriented sessions, these skills are simply more valuable than just about any other skills.
Is this a problem? It could be. If players face an incentive to choose some skills rather than others, the game will track players towards the specifically valuable skills. The result is reduced player choice and increased character homogeneity. I am reminded of the talent system in a alot of MMORPGs. With every release, World of Warcraft designers have said they want there to be diverse builds (skill choices) for characters. Every time, players do the math to identify the one or two optimal builds for each class. While it is entirely possible to deviate from these builds, it typically comes at the cost of top raiding guilds not allowing you to participate in the cutting edge content. If some choices are clearly superior to others, players will gravitate to them.
A Possible Solution to Balance Issues in Narrative Skill Systems
There are ways to address this balance issue.
Of course, you could simply ignore the problem. Narrative skill systems are not built to be balanced. It should not be a surprise that such problem arise. If the players accept that some skills are more valuable than others, then this is not a problem.
One could also generate a set of house rules that empower some skills while disempowering others. An example of this is in my previous post on how to make perception a little less unique by adding a perception component to all lore/knowledge skills. Following MCGs lead, you could also gateway some skills by making them only available at specific tiers or with specific foci options.
I prefer a less elaborate or formal solution. Skill choices, especially in such an open ended system as the Cypher System, are expressions of players' desires about their characters. If a player chooses a skill in "biology," it is because he wants stories that involve biology. This is less obvious in some combat skills -- but a choice to focus on combat skills is suggesting that the player wants to focus on combat. Each choice is an expression of the sorts of stories that player wants to experience.
You can take an inventory of these skills. List all of the skills that your players have chosen. Try to include opportunities to use all of the skills. If the players are choosing mostly combat-oriented skills, then make more encounters combat-oriented. If a player chooses a skill in "music history," think of ways to make music history a part of the story. The skills are exactly as useful as you let them be in designing challenges and stories. If you wanted to make combat skills completely useless, don't have combat (not something I am recommending -- just pointing out the possibility). Similarly, if players have ignored social skills they may be telling you that they do not want social encounters.
As usual, this is best handled through communication with your players. Building on Lex's recent discussion of character preludes, let your players tell you what sort of stories they want to participate in. Skills can act in a very similar way.