Skill based leveling system

I think it already is inherently the case that you level certain skills over time, at least for the rune mage and warrior, because they require quite some training to perfect the runes/combos. And the more you perform a skill the more adapt you become in using it. @Logan just described it in this post.

For ranger and musketeer it’s more the general skill of choosing your ammunition and aiming and not so much skill specific.