I think the issue here is that Havoc Demonhunters are in the limbo of being great at aoe fights and meh at single target. However, a lot of our single target damage is also cleave orientated the prime examples being Fel Mastery + Fel Rush and Bloodlet + Glaive Throw. Blizzard does not want Havoc, or any other class, being the star child of single target and aoe encounters. However in most classes you can nerf their aoe potential and leave single target untouched.
This is not the case for Demonhunters because of the cleave heavy havoc kit. Blizzard can not compensate for this by merely buffing Chaos Strike into god hood. One option to "fix", for lack of a better word, this would be to add another single target attack into our rotation. This would open more deviation in rotation from cleave and pure single target for future balancing. Something as simple as an attack that becomes available after using Chaos Strike a few times, as to not compete with fury spenders, could potentially buff our single target to be on par with most classes while leaving our aoe alone. Another option could be a change to Chaos Blades: Extend the duration, remove the % damage done increased based off mastery, and have it's cool down decreased every time a rage spender crits (excluding eye beam since that would just mean Chaos Blades for days).
In case my original attention was lost in my rambling, the main issue is that you can not nerf Havoc's aoe without nerfing their single target as the kit is currently. Additionally, most talent changes would hence forth complicate the balancing process as they try to ensure one class is not king in a situation. Our cleave plays too much into our single target is the end of story. Nerfing Chaos Strike would not harm cleave situations all that much however a Fel Rush or Bloodlet nerf is a big single target loss.