The Concentration skill can only be used when it's fully charged up. It's a big problem during combat: If the opponent hides behind anything, I let go the Concentration key to save up. (shift key when playing with a keyboard) But if I see another chance to use it, it won't work because I will have to wait it up. I think it would work better if it could let the player use it whenever it is over 30 or 40% charged up. I say over 30% because maybe if it's too low, like 5%, we would have 1 second or so that would be wasted getting into and out of concentration... I don't know, just testing to really know how it would feel. video trying to explain what is bothering me:
I also posted on reddit