Dunno about that. Maybe for some. I'm a pretty good campaign player and Legendary thrashed me pretty constantly. Some of the ending encounters in particular were just brutal because they didn't supply the right weapons for the enemy.
The only encounter in my Legendary run that I skipped over was the pack of high raking, dual-wielding Elites guarding the exit of the smelter facility on PoA. I exhaused all my DMR ammo on the Grunts and Jackals, and then went looking for more. And there isn't any. Two racks of Assault Rifles (three each), a few shotguns, and some plasma weaponry strewn about from dropped Covenant, but no long range or precision weapons at all. The door to the earlier part of the level gets sealed shut behind me. I spent an hour trying to either find some ammo or drop just one single Elite, and couldn't do it. So I snuck around them, and when they were distracted by Emile shooting a shotgun at them from 20 yards away, I sprinted past.
The kicker was they noticed this, and all three came after me. Which meant the next check point was me with an AR and plasma pistol against a pack of Skirmishers, two Hunters and three dual-wielding super Elites. Needless to say, I broke the windown and hopped through that, also skipping the Hunters. I hear the sound of Emile getting his ass kicked by that horde for the remainder of the mission, until he teleports into the MAC cannon at the end. :lol