Thievery unlocks sneaking via special training with Bianca. which makes the party invisible for enemies for a while, duration scales with level. Backstab will be an extension to that skill (in order to progress Bianca's story you need at minimum 5 thievery)
I know I'm going to get a lot of heat for expressing this very controversial opinion but it has to be said.
What you've just stated about needing a minimum of 5 thievery in order to progress Bianca's story is one of the main reasons why I have remained ambivalent toward this game's talent system.
Armour Proficiency is a talent that is used all the time in the game - decreasing the amount of damage that a player takes on during combat. Combat being one of the main/primary elements of this rpg.
Hunting is a talent that is used all the time in the game - allowing the player to better hunt down and skin the various wild life creatures found throughout the game. And by "various," I mean just rabbits, deer, and wolves.
Constitution is a talent that is used all the time in the game - decreasing the amount of rest a player spends on tasks such as farming, hunting, skinning animals, chopping trees, mining ores, and even fighting in combat.
Strength is a talent that is used all the time in the game - increasing the players chance of success for activities such as chopping trees, mining ores, intimidating others, breaking down doors, and hitting enemies harder.
Thievery, on the other hand, is a skill that is used very occasionally. It's good for picking locks and that's about it. Now I know people will state that it can now be used to sneak up on and/or past enemies. But here's the thing:
When you've hit level 10+ on each of the three combat skills (Armour Proficiency, Constitution, and Strength) and you also have a lot of the health items (healing potions, healing tinctures, bandages, and food) in your inventory, I've found there are very few enemies you actually need to sneak past.
In addition, most of the time, a player is able to quickly walk past and/or around certain enemies he does not wish to take on.
So then 2 questions must be asked -
- Why should a player invest the time it takes to gain 5 whole levels, just to upgrade a thievery talent that is barely used throughout the game?
- Why should a player have to choose between spending valuable talent points on a skill that's only really useful for progressing the story of a girl he likes vs spending those talent points on more useful/profitable skills?
Ultimately, I think this game's talent system is really unique and interesting. That being said, it is not without faults.
And making players spend lots of time grinding a talent they'll barely use outside of a single character's story arc is definitely one of those faults.
(P.S. I know that you technically, only have to grind for 4 talent points since the first thievery talent point is free! But this factoid isn't really important to my overall point.)