Really great summaries. I agree with your analysis and conclusions.
I feel that the first step is going to be adding skill point requirements for ability use.
Once that is done, the defensive stats needs to be tweaked, I like the scaling flat bonus and percentage bonus suggested earlier, with some tweaks to the numbers of course.
My individual suggestions for skills.
Dual wield - remove critical chance, increase damage to 4%.
Single handed, increase accuracy to 3%
two hand - remove critical damage component.
What if they swapped the critical bonuses for Dual Wield and two-handed like so:
Dual wield - +3% damage, +3% critical modifier
Two Handed - +3% damage, +1% critical chance
That means that dual-wielding daggers gets a benefit from the second property, instead of the critical chance going to waste for backstabs, and Two-handed weapons are a bit less powerful when they crit.
I guess the downside though is that between Scoundrel and Dual-Wielding, the critical damage modifier will stack up a lot more. Perhaps too much more?