I have recently tested the co-op gameplay with a buddy of mine. Overall we had a great time but there is one major pain point that really does not respect player time and I don’t understand it.
Gathering resources is very challenging with the slow respawn timers. This not only is for herbs, and other minerals but it includes the creatures and mobs you need to craft weapons and armor. If I want to farm sirens a lot of the time I couldn’t find many or I would have to wait a long time for the sewers to roll over the fog or the shallows. I don’t quite know all the locations but even at these locations it was a low mob count and the item was not guaranteed to drop. This made farming for a gear upgrade feel really bad and I would be required to spend to much time in game to make progress. This is made even worse that crafting said item is not going to always roll the proper enchants that you want to target for a specific build plan. 5 rerolls on blue and 10 on plague gear? Like okay if you limit that why are we also making it so time consuming for mob and resource resets? The other thing to mention is the timers on the crafters. I didn’t like this as well but I can imagine it would not be as bad if the mobs and resource spawns were more frequent. I can just load up a few crafting benches and go back out doing what is the most fun part of the game which is the combat. I’m sure many others feel the same, and most likely some do not. But I hope the developers consider and value a players time and not make a game that is designed to slow your progress down or make it take all day it feels to accomplish very little.
The costs in materials to upgrade weapons is completely fucked, and the same goes for crafting weapons and armor, the devs have for some reason given each creature drops 3 different items that do the same thing, Mermaids drop skulls, ail and tail; Wolves skull claw and flesh; Bears, skulls, paws and hearts.
And completely randomly the weapons or armor require one material or another to be upgraded or crafted.
It is a system that makes no sense, because of this system it is always better to use a high level weapon that you find around rather than upgrade the weapon you have.
I recommend you read these two topics, if you are interested:
Yes, unless you know how to make them respawn sooner like moving/fast traveling between major distant regions (but if you or a friend revisit the area too frequently it can pause the repopulation/respawn timer)
If you are unsure put your character to sleep in a bed inside your house and then walk away from your computer and take a shower or eat or watch a movie or watch YouTube or whatever you want or you can always enter the crucible in the mean time if you have to play?
If you pick up 1 challenge or bounty at the time you can effectively use them to respawn enemies and resources but it depends on what type of challenge/bounty it is (you want to clear an area before you pick up challenges that require you to kill something also bounties)
Im just sharing these two because this is how i do. 
I think having that friction is required to make the game loop function… literally at all. If you killed a wolf and got all the parts every kill and got all the wood and iron you needed with just one pass through the world it would kill the game loop. You’d finish getting new gear and upgrading old gear in hours rather than days which would make the game pointless.
Diablo 3/4 made the friction to getting gear so low that you can finish a character in less than a week with almost perfect gear if you play for 3-5 hours a day. You don’t want this game to go down that path. Getting loot feels good when it’s hard to get loot. When it’s easy it feels like nothing and nothing is very boring.
I’m writing a detailed topic about these problems, it’s not just a drop rate problem, even if I’m sure the drop rate is too low, it’s a communication problem with the player.
It’s okay to work hard to get something but it has to be something worthwhile, it seems like the game requires a lot of work to do simple and banal things, like crafting a weapon you’ve already found, and so rather than trying to use the crafting system it’s always better to find weapons randomly.
Sorry if I’m vague but if I try to explain myself I’ll end up writing the whole topic here xD.
if I remember I’ll send you a message when I write the topic.