As you get higher in proficiency for a weapon it requires more points per wpf. Diminishing returns as you go upward, one of the reasons why the WM is one of the least effective things to invest in (except for ranged characters which need wpf for things like draw/reload speed & accuracy).
Athletics is important for almost every build - an exception may be a dedicated cav player that is planning on being mounted most of the time. Having a healthy amount of athletics will help you keep decent footwork and not be overwhelmed as much in melee, and it will also help get away from enemy hordes instead of getting surrounded and destroyed.
That said the important part is having enough athletics to compete in general.. I'd say no less than 3 and no more than 7 should be your range, to taste based on your preferences.