After finishing Halo Infinite on campaign and right after playing all the others (besides 5) on Legendary as well. I would say this felt pretty balanced for Legendary.
Really had to change strategies several times with boses but it felt right. Had to have a plan, switch weapons, learn the tricks for all equipment. I.e. it made me really learn the game and its sandbox to get through. Other games I had to just memorize jackel sniper locations, or cheese it.
It was tough, but in the end felt mostly fair.