Some observations on talents...
the current structure for skills
A1 AB1.5 B1 BC1.5 C1
A2 AB2.5 B2 BC2.5 C2
A3 AB3.5 B3 BC3.5 C3
Where AB1.5 requires A1 and B1 as prerequisites, etc.
I don't really see the point of having the "in-between" skills which require two different prerequisites. This kind of structure really only makes sense where the in-between skills provide significantly greater benefit which thus justifies 2 prerequsite skills vs. the more usual 1.
Recommend simplify the structure make a more simple progression for these skills.
Thief skills and balance... Overall, I'm very unexcited by the PC thief choice and thieves in general. I don't view most of their special abilities as terribly useful and none really stand out the way Loren's dual wielding or the PC's healing ability stands out.
Also, the thief fails as an "in-between" class that is equally good in 1st row or 2nd row. They are good 2nd row bow wielders (only).
Compare thieves to mages (very biased to 2nd row) and fighters (very biased to first row).
I would suggest a dramatic revision to the thief class to give them the ability go both ways.
Some suggestions for basic talents (replace some all existing):
1) Significant defense +25% +50% +75% (note these are disproportionately high to make up for inability to wear heavy armor)
2) Any and Dagger dual wield - same as Loren, but off hand can only be dagger
3) Steal - +10% +20% +30% gold recieved, equal chance to get an extra gem drop
4) Treasure Finding +5% +10% +15% of extra item
5) Bow expert +10% +15% +20% bow damage
Note these are all passive, active skills would be found in specialization