On Heroic. It's actually pretty fun because it isn't [i]too[/i] hard but it still makes covenant much scarier. Also, anytime an Elite whips out a Concussion Rifle, your life will be hell for the next few hours as you try to kill him. And Hunters are almost unkillable. You know what, AMA.
Lol, found Heroic to be kinda easy tbh. Only hard parts were when there were either -blam!-tons of brutes or elites.