Three tips for legendary would be
Dont get frustrated, and take breaks after every level
Run past as many enemies as you can
Plasma pistol headshot weapon, (Preferably DMR or Needle Rifle)
I also did the last level first on legendary, makes everything else seem so much easier
With hunters u can get a needle rifle and stand as far away from them as possible and just shoot them in the stomach, just above the shield. When u see a bit of the orange blood it means you got them, and just keep shooting that area. If you are far away enough they won't even move, and they'll just keep raising their shield, so just keeping shooting that same spot when they drop their shield. Once you've burned through like 6 clips or something they'll die, so make sure everything else is dead before doing this
