You're perfectly right about the xbow historical notions. My regret was not about historical accuracy, but about the fact that crossbow abilities don't crit. I know, maybe it'd be too powerful, but still... Anyway I'm approaching the definitive version of my build (according to my tastes, of course, some may disagree...) It'll have marksman and scoundrel, but maybe even that 1 single point in some elemental magic (fire comes to mind due to burn my eyes for example). Still tinkering on that. On the steam forum I also got the suggestion to take every element at 1 point...
Another thing I like is sneak, but the changes in EE made it worse... no reduction in AP cost while levelling the skill, only reduction of the enemy's cone of sight... pity that.