Aw nobody want to watch and analyze your gameplay. This is MY time to shine!
Disclaimer: This is from my own point of view and personal experience. I am by no means a pro player, but I’m no casual either. I play too much video games so I am naturally gifted. I never strive to be the best, because my time playing is for my own enjoyment.
Also, I write messy, so I might be all over the place, but I will do my best to try and keep it readable and understandable.
Now enough about my life’s story.
First thing I noticed in the very first encounter is that you are reluctant to engage. You go in, do a couple of chops and then back out. My initial reaction was “be more aggressive”. You’re a Zealot. Either you’re in the front lines, or you died going there.
Second though, which I already had reading some of the comments. Are you McLovin’ your loadout? I find both shotgun and tactical axe to be, not very good. At least in my hands. I’ll admit that there has been some time since I last played either. My Zealot runs knife, heavy evis or combat axe. I dabble with Crusher from time to time, but it’s not a favorite. Guns are the obvious Columnus Mk5, or Revolver.
You can without a doubt make anything work in the game. I just find that certain weapons are a lot harder to do so with. I, being lazy, gravitate towards the ez pick. 
Keep moving. I recently made a tutorial and gameplay video for my older brother, who plays a little Darktide, in order to help him out. I commented how “you always need to be moving, never stand still, always dodge, are you picking up ammo? Dodge. Enemy behind you? Dodge. Walking in a straight line? DODGE.”.
I notice this with you as well. You have moments where you stop in your tracks. And you don’t dodge nearly enough. Dodging is free and regenerates after about 1 second after your last dodge. So dodge away!
I saw comments about this as well. Situational awareness, or as they said, “head on a swivel”. Listen to Specialist and Disabler sounds. They are all around you, netting friends, throwing grenades etc. In Auric T5, you can have an insane amount of specials and disablers active at the same time. It is very much key to be able to… Disable the diablers before they disable you! 
This was something I learned through my hundreds of hours in Vermintide 1 and Vermintide 2. Specials, as they were called there (in Darktide we have them separated as Disablers and Specials), were the biggest danger to the group. You’re 4 man strong, as soon as 1 player is diabled mid-horde + monster + 4 Maulers + 3 Crushers + 4 Bulwarks, you lost a HUGE amount of help.
That’s why it’s so important to, listen, hear them spawn in, turn around, 1 tap and back into the fray.
Another comment about movement. I see you being out of range for melee combat, swinging your axe and walking forward to the target. The problem is that your movement speed is reduced while swinging. Instead, stop swinging, walk/run forward and start swinging. Or like the cool kids do, run and slide into combat like a hero. Which also gives you the added “dodging” modifier while you’re sliding.
Chaos spawn is my least favorite monster. I never really learned how to deal with it effectively. I mainly try to not get grabbed. If you see someone getting grabbed, you need to get close so it starts to swing. That interrupts it from regenerating health and will drop your buddy (which was you in this instance).
Another thing I do is I dodge around an object. It’s easier to avoid attacks and grabs then, because he will still attack and grab at you through the object, but you always have a little more room to avoid being hit/grabbed. I’ve also been successful in using elevations. As in, run up a ledge/stairs/whatever, then jump down.
But like I said, I never got good at it. It’s a little bit luck, a little bit skill. Or as I like to say. 60% of the time, it works, every time.
Pushing the Chaos Spawn does nothing but deplete your stamina.
Ammo crate. Not sure if you or your teammates are aware of this. Ammo crate has 4 charges of 100% ammo. So each time you pick up ammo, it loses a charge, no matter how much ammo you were missing. In my experience, it seems a lot of people aren’t aware of this, even in T5. I use a mod called Ration Pack (Ration Pack at Warhammer 40,000: Darktide Nexus - Mods and community), which allows you to see a colored number above it, indicating how many charges are left.
On Heresy, and in your situation at 27:44, it was no biggie. I just figured I’d poke the subject as this is a “request for learning”.
31:24 of the video. In my opinion, never go close to a Poxburster that has jumped down. You can’t push it while it’s on the ground and it’s prime realestate to be shot from a safe distance. As the Psyker did and he also went “BOOM! HAhaHAHahahA!”. 
I see this in T5 as well, I think it’s an unnecessary risk. Dispatch of it as quickly as possible so it’s not a threat.
Ability usage. You use your F ability very rarely. It’s there to be used. I’m also not sure if you have the talent that “crits give you 1.5seconds off your cooldown”. Combined with tactical axe, which has increased crit chance, it would give you your F ability back faster. Meaning not using it, is even more of a waste.
This is personal preference. You are free to play your Zealot as you wish. I tend to mainly do melee, as where you tend to do ranged combat. Nothing wrong with that. Though I think that Zealot are very good meleers. This is partially a throwback to the “be more aggressive”-point I made.
I realized this is probably why you don’t use F that much either.
Okay let’s try and summarize it all and try to not sound too negative. I think you did well. It was an eventful game where you almost wiped several times. That one poor player pulled Demonhost TWICE and paid the piper both times. 
I think you did a good job at reviving. Also, it was good that the entire group didn’t blindly focus the monster. That’s something I always did in Vermintide. One person can handle the monster, the others can handle the horde and specials until it’s safe enough to go back to the monster.
This happens all the time in T5 where 3 players go and have fun with a monster, while the fourth player is left to handle everything else. I think it’s risky and unnecessary.
I’d also like to add that there are modifiers in T5 that makes them feel more like T4, and modifiers in T4 that makes them feel like T5. Lights Out, Ventilation Purge are both easier in my opinion than Hi-Intensity Shock Troop Gauntlet. There are also Low-Intensity and unmodified missions too.
So once you’re T4, you can basically also play certain T5 missions. And at one point, you just have to try it out. There’s no magic number or time where you are “ready for T5”. Just keep playing, keep killing and eventually you’ll be bored because Auric T5 is too easy and you’ll still on Steam forums all day and complain how Fatshark doesn’t update the game fast enough and the game is too easy.
I can’t be bothered to read through all of my nonsense so I hope it is some help, if not, 
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Oh last edit entry. Since you are already using mods, I am going to give you a sCcaAaaaaRrrry suggestion! Scoreboard at Warhammer 40,000: Darktide Nexus - Mods and community. People love it, people hate it, people argue about it.
I think that, in order to understand your efforts and gameplay more, you need to have some sort of performance metrics. It doing most damage doesn’t mean the bestest that ever was. But doing 1/10th of the damage of everyone else, is an indication of “not pulling ones weight”. I suggest you use it for personal betterment and not for belitteling of others.
