There are three ways to kill Hunters very quickly. The first is a Rod Gun, the second is a Human turret and the third is a sniper round to the back.
If you have neither then your best bet is to grab double SMGs and backpedal away, wait for the Hunter to Melee attack and then circle it and fire on the orange part of it's back. It should immediately try to hit you as it turns. Because the Hunter is leaning its weight on this attack you should definetly avoid it, espically on Heroic and Legendary.
Circle it once more and do the same. Repeat until you kill it. If it begins to fire it's Rod Gun then move close so it will cease to fire.