It's probably a rotation issue or you may be using roll/sever tendon too often. I can typically maintain 60-80% in sustained combat, but if you make a mistake at any point its very easy to find yourself dry.
I only roll whenever I need to vanish out of combat, other than that I don't use it too often. I don't trust my teammates enough to roll all the way to the ball in HB and throw it back so that's out of the question lol. I only use sever tendon when I need to stop an enemy from leaving prematurely, it may be an issue on my part. I might have to change my rotation a bit to help with this. if anyone has any tips for me, I'm all ears.