When I bought this game, I was under the assumption that the classic playlist would include classic settings. one of the biggest annoyances has been bloom.
With 85% bloom - It allows us to spam more than we use to, but still includes the randomness that 100% bloom has. Unlike previous Halo titles, when I pick up a kill with the pistol, I have to pause for the bloom to reset before putting 3 more shots on another enemy. The only factor of time that should affect my ability to kill is the rate of fire on the gun, not some artificially imposed limit.
With bloom in general - it gives a big advantage to crouchers over people who like to walk around on maps. Players have little incentive to move out of their bases if they can just wait to crouch-spam someone trying to be aggressive. And because crouching is usually followed by hiding and peek-shooting, it slows down the game tremendously.
More pistol ammo - With the ability to fight mid to long range battles with the pistol, you become completely helpless after running out of ammo. The assault rifle is all but useless when trying to run around the map and grab some more ammo.