So, to the OP's point, to recap:
You don't roll:
Ceremony
Form Resistance
Parma Magica
Penetration
Some are almost never rolled:
Teaching
Magical Meditation
Some are seldom rolled:
Animal Handling (depending on some Supernatural powers and the focus of your character, maybe)
Magic Theory (for Insight. It might be rolled in some adventures, as well)
Living Language (and Dead Languages, though some research or poem-crafting characters might do)
Ha, well, it is a very bad virtue, but at least this discussion has produced both mathematical models and some suggestions for its improvement!
A similar previous discussion is here: Puissant vs Learn from Mistakes
To review the rest of the present discussion:
•it is much worse than both Affinity and Puissant
•can only shine if you miss by 1 or botch at least once with the same ability, which implies:
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an obvious handwave. How are you or your companions surviving consistent failure or catastrophic failure?
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you have to roll a lot (a lot!) to consistently have good odds to earn the 5 xp. You also need a skill that has many many different difficulty levels, and ways to manipulate your total too, as your skill may rise to the point you can regularly only miss if you botch. And you may need a group that role-plays a lot of adventures, with multiple sessions, rather than some more abstracted, long-term Lab-ensconced hermit advancement.
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you have to survive your fellow Players/Magi/grogs/Companions tolerating you interjecting your character who obviously and demonstrably has failed multiple times previously in the same sort of situations. "No, I'll scout ahead!" "No, I'll bargain with this guy, I am really good at this." " I'll sneak into the guard tower, I am a natural at this, I swear, you guys." "A'ight, I am gonna charm the breeches off of the duchess, just give me a couple of hours."
They might just take you behind the outhouse and quietly murder you. Specially if you missed rolls by 1 and refused to use Confidence.
•What NPC can take this? xps are already an abstraction, but this virtue depends on participating in stories, and specifically sessions. Do you give this NPC an extra 5 xp in that skill every 2 years, and a very bad rep for failure?
Best skills for making certain this virtue earns you the xp each session I believe are:
•Concentration, bar none! (in the link above, I suggested a character concept with Flawless Magic, Magic Addiction, etc. Essentially, each spell is multicast with a stress die (Flawless magic) in situations which trigger Concentration rolls; magic cast triggers Magic Addiction rolls each time. This magus also has MuVi spells to modify his spells, and you cast these as well, which trigger both MuVi Concentration rolls, as well as the other Concentration rolls. Concentration checks can be increasingly more difficult (and in combat start out at 15!), so you are good there. With Careful with (Concentration), you can avoid botches, and just hunt for "by-1" failures. With both having multiple copies of redundant spells, both for combat and investigation, this character can justifiably, and quietly, fail a Concentration roll here or there without any problem for the Story itself, while rolling dozens of times in 1 or 2 rounds (get an app to have this all ready to roll and not slow things down!)
•Finesse this one is more iffy, as using multiple Rego Craft rolls to trigger the "by-1" failures may not be deemed central or useful to the story by the rest of the Troupe. if they are ok with it, it will be amazing, as Finesse has plenty of difficulties to choose from, many failures/botches will not be life-threatening, etc. You can also use Finesse in combat with Multicast to hunt for those "by-1" failures. Because you want to avoid botches in combat!
•Any Craft/Profession/ability used for Faerie Magic charms, for Spontaneous spells and the like. These do take some time to craft, and maybe represent Fatigue levels lost but can be justified to be used multiple times in an adventure.
•Supernatural ability "X" For charged items from Rusticani using their Craft Magic ability for Supernatural ability "X". If they can live with consistent failure! Best to specialize in a quick-to-craft item. Could conceivably use multiple times in a session.
Other good opportunities to abuse this Virtue may occur to others.
Anyway, good gaming, sodales!