I tested this trickster skill several times, it is well enough balanced to have dissuaded me from doing it several times as the risk was high for the story. Sometimes, to test, I try to steal objects with a rollmax7, I hesitate between 8 and 9 and from roll10 I avoid. after roll10, the item is not worth the risk of causing combat or even just losing reputation with the npc. In addition, once the trickery is successful, there is still a waste of time in the story when the npc investigates the group to find the thief.
In short, I find that this trickster skill is very well balanced, to deter exaggerated trickery.
In addition, the pickpocketing is very interesting when it allows a strategic alternative to the story, when the npc has on him a quest item, a compromising letter or a potion that would allow the possibility of creating a new path of decision to the gameplay.