Let me start off by saying that I enjoy this gamemode overall and I think it is a very good addition to Halo 5, still should have been in at launch, but there are a lot of problems that exist in the mode that severely hinder it form being as best as it can be.When people complain about the difficulty I think these reasons are what they are complaining about as some of the problems make some rounds simply undo-able and that is not a measure of skill, it’s just a lack of balance and no fun. I think if these problems are fixed then it will be a much more fun and enjoyable mode.
1. AI Are Bullet Sponges: I hated this aspect of Destiny and do not like it in Halo 5 either. To make the AI or bosses more challenging they should try adding more dodge and defense actions as well as THE USE OF COVER. The AI overall never do anything except for sit in one spot and move around in a small radius while sitting in the open eating bullets, for good reason as they can eat a lot. At the current state the AI feel as if they all have mythic level health. This is not just for the bosses but for their ads as well. I think the health of all enemies should be equal to heroic-legendary difficulty and give them more attack and defense options and the ability for cover usage.
2. The AI have incredible accuracy: I think everyone has had a moment or time where they are incredibly far away or dodging an attack from an AI but it can not be dodged due to their lock on auto aim weapons. The AI seem to know how to make every single shot connect even when using automatics, I once had a Promethean soldier using a saw that was able to kill me in a ghost as I was doing ramming runs and trying to get away from him but somehow he was able to continuously shoot me with the saw for 4 seconds without missing a shot and while I was boosting away atleast 50 meters. They also seem to be able to use guns for longer range then the guns are capable of doing when in the player’s hands. Reduce their accuracy by about 25% I would say and make that percentage increase for every 5 meters away the player is so if I am 50 meters away from an AI with an automatic his accuracy percentage is around 50% or less. PS. Nerf the Phaetons as their primary gun does not miss a single shot ever when you are within their line of sight.
3. The damage output of the AI is TOO HIGH: The Damage output is close to being correct but not quite there, of course a large problem of the AI damage output lays with their godly accuracy. Nevertheless, I think the Enemy Damage should be reduced by around 30% and increase in damage by 10% as every round goes on. I do not like how any AI regardless of what type they are is able to kill me in 0.1-1 second. It seems silly that I should have to run away from 2 soldiers in round 2 because they can kill me so fast, also get rid of their teleportation. No on likes it, make them use cover instead.
4. Some Rounds are simply not possible at lower levels: When round 2 has an objective of taking down four banshee raiders that kill everything on sight instantly, there is a big problem as no one quite has the reqs to take them down within 5 minutes. I’ve had a game before where we had two warthogs out trying to damage them but with their accuracy and damage output the warthogs were no chance and their ads guarding them in ghosts were making it even more impossible. The Wardens on Round 3 on Apex 7, nothing to be said there, I don’t know who thought of that. The wardens spawning on early rounds are not possible. And if it says to kill 75 soldiers. Spawn 75 soldiers in at once. Not 5-10 soldiers with a couple dozen crawlers and 4 knights and then making us kill all of them before spawning more in. If you are going to do that then double the timer.
5. Near Impossible-Impossible Boss Rounds: This is another one that I have heard almost universal agreement on. Atleast in the beta the bosses spawned outside. Now whenever the bosses consist of three bullet spongy insta kill wardens they are inside a small confined space that protects them from all vehicle damage and their constant spawning ads can almost kill scorpions in seconds. I don’t know how any of the developers thought this was fun or smart when designing the mode. 343 Dev: “Oh I think it would be great if on round 5 a mantis spawns inside the garage where no vehicles can damage him and then we spawn 10 knights with legendary incineration canons that keep spawning to defend him. I think the players will love almost never being able to beat this round unless they spend 14.99 to buy more powerful reqs.” The boss spawns on the final rounds are in the absolute worst spots end of story. They are always inside and always surrounded by incredibly powerful ads, usually knights. Please spawn all bosses outside so we can actually win the round, and please not so many knights. Pipap Deacon is near impossible in the time frame given he has so many knights helping him out and he has his own lock on needle rounds that will destroy your vehicle with ease.
6. Make Weapon Reqs useful: Right now weapon reqs are useless due to not enough damage output and the incredibly small amount of ammo. I think to make weapon reqs useful they should be good for an entire round of WZFF that way a rocket launcher will actually be useful against the warden. Either make them have three times as much ammo and the ability to refill it throughout the round or unlimited ammo for the round. Even being able to refill it a couple times at a req station would be a lot better then the current setup. Using a weapon req is entirely useless.
7. Respawn timers and Spawn killed: Not much to be said here. Respawn timers are too long right now and afterwards we respawn too far away from battle to be of much help. Please reduce spawn penalties, or make it so the timer only increase if you as a player die individually. If I do not die once until round 4 my timer should still be 10 seconds. On the opposite end I have been spawn killed in vehicles many times due to the AI being right next the vehicle spawn points or the phantoms with indestructible guns shooting at me after I leave the garage.
This Video shows off many flaws all at once, this was my only banshee 
https://www.halowaypoint.com/en-us/games/halo-5-guardians/xbox-one/game-clips?page=1&gamertag=MasterAndChief#ugc_halo-5-guardians_xbox-one_gameclip_MasterAndChief_4e578da5-b091-4cb9-8cda-f8d13825fb34
I think if you address these complaints 343 then you will have something truly special in your game and if you want even more players returning and more longevity in your game then adding classic survival based firefight would cater to a lot of the veteran players and be something cool and new for the newer players. Anyone reading this feel free to give more suggestions and ideas, but please back up ideas or criticisms 
I understand that teamwork can beat almost any round but I should not have to communicate with all 7 randoms to be successful. This is a matchmaking mode with random people. Many do not have mics or many are already in parties.
Thank you everyone for helping this forum get a lot of traction! I hope 343 reads this now with all of your feedback and criticisms as well!