Rage skills levelling - how does it work?

[Karlos]

Originally Posted by Mandea

unfortunately, you can't speed up their leveling like you did in AP/CW (there were some skills). Now you just have to use as much rage as possible (so it seems so far).

Yeah, seems so, the question is - is the levelling based on how much rage you spend? Or what skills you use? For example if you use vortex all the time levelling will be slower than using different skills? Because in later game levelling is noticeably slower and it would make sense for the newly obtained skills to level up faster somehow, to catch up with the old ones.

I wish the manual isn't as useless as the previous ones. Oh well...