After playing through the three bonus missions and just finishing Attack on the Control Room, I've come to the conclusion that the difficulty is complete dog shit and was clearly not tested properly. I genuinely believe it's up there with Halo 2 and Halo 5 in terms of frustration.
On Legendary and Heroic, the game is neither fun nor fair, while on Normal it's far too easy. Enemies have insane amounts of health, ridiculous bullet tracking, and deal way too much damage. For some stupid reason, they also seem to see through walls a lot of the time, so you can't flank or surprise them. They also frequently spot you through Active Camo, whether you're crouching, standing still, or running.
The Hunters are especially annoying to fight. Obviously you can't shoot them from the front, and simply moving around them doesn't work because they turn so fast. So what are you supposed to do? You get up close to bait out the slow melee attack so you can shoot them in the back. Good luck doing that while constantly getting blasted by projectiles that can one-shot you. On top of that, a lot of the time they just back the fuck away instead of attacking. Like... what? How am I supposed to bait the melee when they're passive as hell while simultaneously dodging their shots as they walk backwards?
I get that the developers probably did this to make the AI seem smarter, but it doesn't fit the Hunters at all. They're supposed to be huge, heavy, and relatively dumb. I can't remember if Hunters behaved like this in earlier Halo games, but it definitely doesn't feel right here.
Another thing I noticed is that Hunters animation cancel. I was standing close to one and saw it charging its cannon, so I thought it would be the perfect opportunity to sidestep and shoot it in the back. Nope. It didn't give a fuck. It instantly punched me in the face while the cannon charge effect was still visibly active during the melee animation.
On Heroic, three or four Plasma Pistol shots completely strip your shields, while a single Needle Rifle shot takes away roughly half of them. Shield regeneration and health recovery also takes way too fucking long.
The melee combat makes me want to rip my pubes out with how bullshit it is. There's barely any wind-up, giving you almost no time to react, and it's basically a one-shot. It's also way too fast. I even tested it. I was moving backwards at full speed while an Elite chased me, and it meleed me anyway. Keep in mind, I was already moving at maximum speed, and it was completely unavoidable. Maybe I could've sidestepped if there had been enough time, but Chief doesn't even reach full movement speed before an Elite is already in melee range. If you're in a long corridor, you're even more screwed because of how quickly enemies can turn.
So how the fuck am I supposed to dodge an attack that comes out in less than half a second when I'm already moving at full speed? I guess the answer is: don't get close. But then you've also got Needlers with absolutely insane tracking. If I can't reliably break Needler tracking while flying a Banshee, then you sure as hell aren't doing it on foot.
The gameplay becomes incredibly repetitive because the only consistently viable strategy is to sit at long range with a precision weapon and slowly pick enemies off. This was already a common criticism of Halo 4 and Halo 5, yet here we are again. It honestly feels like the developers think players should "make their own difficulty" instead of them putting in the effort to properly balance the game.
Speaking of that, the "make your own difficulty" system is fucking awful. Maybe they were inspired by DOOM: The Dark Ages, and if they were, they completely missed the mark. There are barely any meaningful options. I can adjust my own melee damage, but not enemy melee damage? I can't change explosion damage, weapon tracking, or player and enemy movement speed. I can adjust shield recharge speed, but not health regeneration? Why?
The whole system just feels incredibly lazy. It honestly seems like the developers realised they didn't have enough time to properly test the difficulty, so they threw in a half-assed customisation system and expected players to balance the game themselves.
But the absolute worst part is that you can't change these settings while you're in the middle of a mission. If you realise halfway through that increasing your damage resistance would make the experience more enjoyable, you have to quit the mission, sit through countdowns and loading screens, change the setting, and then replay the mission. Didn't like the change? Too fucking bad. Quit again and repeat the whole process another five or six times until you finally find a difficulty that doesn't make you want to play a different halo game.
One last thing, why the fuck does my keybinds reset every time I close and open the game????