Armor system needs nuance, either with a return of saving throws, or ways to increase armor penetration. For example, Necromancy could also increase the % of armor that Shackles of Pain or Decaying Touch could penetrate.
Personally, I think my favoured solution would be to have a single form of armor - physical armor - that stops most physical effects (which would include, for example, the giant boulders of Geomancy), and replace Magic Armor completely with a resistances+saves system.
The only issue with that is that it would require a lot of work to implement at this point, I think.
But I also think that it's a great idea to have skills have more varied effects from having points put into their abilities.
Talents are more a set of smaller problems than some larger problem. I'll definitely be scripting new effects onto existing talents (for what it's worth, I think ambidextrous is a great concept, and it kind of makes sense. Try throwing a grenade with your non-dominant hand and see how quick and accurate you are, eh?)
I think Ambidextrous is a cool idea for a talent, I just don't think it's worth taking it, since you'll lose out on any and all bonuses you would've gained from putting something useful in your off-hand. I also think that it's an extremely odd choice as a name, because Ambidextrous means that I should be better at actually dual-wielding, but it has nothing
to do with that.
I'd call it Fast Pockets
or Quick Draw
instead, and have it apply no matter how many weapons you happen to be wielding, or how. I'd then create a separate Talent to incentivize the use of duelist-style single-weapon fighting, such as "Duelist - Doubles the bonuses and modifiers of a single-handed weapon, but only as long as your off-hand is free. Also adds a 5-10% chance to parry enemy melee attacks"
or something to that effect.
Personally, I really fucking love the concept of single-weapon duelists for some reason, but they always tend to be forgotten, whereas the near-absurd dual-wielding spiel is in every game. And Ambidextrous sure as hell isn't going to get me to sacrifice a whole equipment slot just to get the cost of scrolls and grenades down - grenades and scrolls that aren't even useful most of the time because of the round robin turn orders and the armor system.
But yeah, Talents are indeed a set of smaller issues, which is why I had to stop myself from going into each one in the OP, but merely address Talents as a systemic issue. The individual talents themselves and what should be done, what can be added, what should be removed, etc., is entirely debatable.