For example, take the idea of athletic talent, artistic or intellectual genius. We have absolutely no idea how a person comes to possess these traits or how to measure them. For every genius that just demonstrates a natural affinity for a certain skill and works on fine-tuning it, there is a genius that needs to train very hard to get to their level of mastery (so they have the raw ability, but are in a field requiring them to train it so that their genius can reach its' full potential).

Berowin, for example, says that she has something like a Talent for Shielding; but she implies in the same scene that she practiced it for so long that it contributed to her mastery. While this is a good character to keep in mind since her Talent or high degree of skill with that weave turns the general understanding for how Shielding works on it's head, it is not beyond belief that she is a below average channeler in all respects save some aspect of her thought process that makes Shielding in particular a weave that she conceptually and instinctively understands and knows how to manipulate. She simply "gets" the weave, and has worked on fine-tuning it so she knows exactly how to manipulate the displacement energy fields effect so that stronger channelers can be held by her.

Maria regarding Talents:

So it seems to me that Talents are not quite genetic and the overall cosmological balance can determine whether a Talent can be expressed. There may be millions of Talents that just aren't being seen during these times because Tarmon Gaidon is so nearby, and the Pattern has no need of them. I think it is easy to imagine many Talents existing during the Age of Legends that would involve manipulating technology or ter'angreal that just don't have any place in the Third Age, so those are either undetected because there is nothing for them to interact with or the Pattern is suppressing them.

I don't think having a Talent in a weave or technique has anything to do with other weaves or the flow that weave uses. Having a Talent for Compulsion doesn't imply that you have any kind of strength in Spirit, creating wards, Bonding or etc. For most intents and purposes, those are all unrelated abilities. Rand is a good example of this - he has many Talents of his own, but when you compare him to Aviendha, Nynaeve, Elayne and Egwene, he doesn't automatically gain access to Talents they may have just because one or more of his own require the same flows or are related (i.e. just because he has a great strength in/a Talent for Air, doesn't mean he can Listen to the Wind, as Nynaeve can, or even that he has a Talent for working the weather).

From what I understand of the mechanics of Linking, while the Leader can draw on the combined strength in the Power the group contributes to a unified pool, only the Leaders' Talents can be used. This seems to be why Circles were such a high science during the Age of Legends; complicated feats would require a well-balanced Circle in which the leadership would be passed to different members of the Circle as their Talents and skills would become needed.

Since the needs of the Pattern are in the mix, I'm not sure if the mechanics of Talents will ever make sense - we do have a rough idea for how Talents work, and for all intents and purposes, having a strong Talent often requiring developing it. Nynaeve has the strongest Talent for Healing in the world, but she has been outperformed by weaker channelers that have been trained in her methods - perhaps because she hasn't developed other areas of channeling to the same degree, so she relies on her raw skill instead of using all of her potential. She's much stronger as a Healer now after we've seen her practice the different skills than at the beginning of the series - she would never have discovered how to Restore a Stilled man's connection to saidin if she hadn't practiced Delving as much, and this later came into play when she discovered how to undo Compulsion and then Heal taint-driven insanity. Her Talent remained the same, but she had the practice and hence experience to really maximize it.