Since the patch, the willpower system is having problems. I used 30 points to be flexible, but when I was jumping, my stamina no longer recovered. I had been jumping all the time, but my stamina would not recover at all, I think it was a bug.
You mean the stamina recover while on the air right? I use agility build and noticed that aswell, but I think they patched that to be honest, as it can be quite op just jumping around with endless stamina, its a bummer to lose that, but its balanced this way 
I think it’s a good attribute to restore endurance in the air. Because you need 30 points, and you can’t add other attributes.