At first I would like to apologize for my bad english. I will try my best. And, because of my bad english, i will not be able to widely expalin all my thoughs, unfortunately. But lets start.
I played a while with my friends (about 300hrs of my 900) and found a number of problems with current state of multiplayer, and some of them really annoying. I wont discuss here tech isuess, but rather gamplay issues.
Multiplayer its waaaaay to easy. There some posts on forum with calculation and somewhat full overwiew of problem, but beign shortly, monster HP scaling its very unfair to them. Having 2 buddy afk in town, elites and bosses dies almost same as fast, as in singleplayer. I would glad to see some bigger numbers in monster healt bars. We are all looking for challenges. Dont we?
Auras. Some of them have 15, some 20, and some for no reason 12m radius. While i glad to see aura with 20m, it is still looks too small. I really want this QoL change that will make all auras atleast 25m radius. So my teamm8s will be able to kite bosses w/o losing that 100% poison resistance and getting oneshoted by acid/poison damage (yeah we play hardcore only).
That thing with material drops (aether crystals, ugdenbloom) is annoying. I cant even understand, why its drops only for 1 person. This is makes coop farming not just completly meaningless, but even much worse than farming in singleplayer.
There a bit more of smaller issueses that i can live with, but those 3 (especially 3rd) is should be solved asap in order to make multiplayer in this game to the great and worth playing state, imo…
P.S. Feel free to correct my english, i really want to learn this great Language