Dont try and do Malice level mission is you dont know how to play. I'd suggest playing upto level 10 at least before you switch to Malice, that way you know the mechanics and have 2 talents and some gear.
lvl1 is easy, lvl2 isnt much harder but you get a tiny amount of extra XP and more matarials spawn, 3 (malice) is where it starts to get fun, I'm not playing 4 or 5 till i have and organized team and not randos. Assuming it's like vermitide that's where it's really fun and you won't make it through every run.
Stick together, every wipe ive had has been when someone runs off, then someone else trys to save them and gets battered then the last 2 get overwhelmed. 1 dead guy you can recover later, 2 dead you're in serious trouble.
Wait at drops till everyones there, if 3 of you drop and the 4th gets jumped by a special then you cant do anything and they are dead.
Demonhosts are like witches in L4D and should be avoided not killed, they will kill whoever startles them, but you can block it (good for the achivements if you care) while your team kill it. but they hit hard, dodge and block, and a DPS check for your teammates.
Gear isn't purely the big number is better, type of weapon, perks, blessings can make more difference. a 300 bolter can be much better than a 320 bolter depending of the stats and the bonuses, CHECK THE INSPECT TAB on an item to see how its stats work. The little bars are only an indication.
Performance wise, not trying to flex (but its going to look like it anyway) but i havent seen the issues people are talking about, I run 4k everything maxed incl ray tracing with DLSS3.0 on quality and I sticks around 120 fps with very little hitching, that said im on a 13700k and a 4090 so yeah i can see it struggling on lesser machines.
Thats said it also looks amazing on a 65" OLED TV, The next monitor i buy will be an OLED, it makes games with light/dark HDR look soo much nicer. and doing a dark mission with lazguns blasting is fantastic.
The game crashes, a lot, but you can reconnect to a mission if you fire it back up.
DO NOT waste your materials upgrading items till you are 30, and the make sure the shop has reset before you buy things after leveling up, they are on a timer and dont refresh as you level, only when the clock ticks over.