I have no idea if this would work but it is in fitting with the characters story of an internal battle between competing calm and bloodlust (discipline and hatred).
What if the resource Hatred was to regen faster when being hit (or over longer kill spree's or both) and whilst hatred begins to regen faster, discipline regens slower. (perhaps it could even be based off a enemy proximity?)
The idea being that when the demon hunter is at the back controlling the battle from afar, the demons hunters prime resource is discipline. Controlling a battle from afar would require calm and discipline. During these fights hatred regen might be reduced to what discipline regen is currently (or more probably, slightly faster than that, but reduced none the less) whilst discipline is regened at a much faster rate. Under this fighting style, traps and turrets would be prime attackers. ?+a decoy?
Once the Demon Hunter engages in furious close combat fast paced and close proximity, the demon hunter loses all composure and is overcome but the furious blood lust of slaying demons leading to a massive boost in hatred regen and a greatly decreased discipline regen.
If you start a fight in a Hatred oriented attack and feel your coping too much, simply vault or run out and let your characters regens start to swing as you do more disciplined attacks.
What are your thoughts??? Blue poster input would also be great!