I only have a little over 5,000 hours in this game, but I feel like I have enough game play to give a fair review of it now. You can't go wrong with this game. It is still getting updates from the developers, and it's been out for quite a while. If you like 4 player co-op games you'll love this game.
The largest problem is starting the game. The first few difficulties can be a slog, and the real fun doesn't start until champion. Open your commendation chests, and any other chests up until champion emperor chests as soon as you get them. Your item power increases from opening them, and saving them just slows your growth and ability to get to higher difficulties quickly, and get better chances for red items.
There are currently three modes and, but only two are available without buying an additional dlc. The ones that come with the base game are normal co-op campaigns, and the chaos wastes. The normal co-op campaigns each take about 30 minutes to finish. You will find 3 Tomes and 2 Grimoires hidden in each of these maps and getting them to the end will provide you with more xp, and better reward chests. Picking up a tome will take your med slot. you can drop them and heal if you find a med just remember to pick them up again. Grimoires reduce the teams health bars by about 31% and cannot be swapped out like a tome. You will also lose them if you get completely killed. They can be thrown if you get in a sticky spot and need more of your health bars back by equipping them and then long holding attack.
Chaos wastes is a roguelite version of the game. There are no books in this mode, and completing one takes a little over an hour. However, you will probably get 3 of the highest tier chests for the difficulty you attempt if you make it through to the end. 2 will be highest for sure, but the third depends on maps completed and coins retrieved. You start with just the talents you've earned and white versions of the weapons you start with. You will find blue coins scattered across the maps that will let you purchase weapon upgrades, weapon exchanges, and boons. You can get some pretty crazy builds in this mode and it's a lot of fun.
The third DLC mode, is not played much by the community and usually is looked down upon. It is only available through the purchase of the Winds of Magic DLC. It has a few unique modifiers like lightning strikes, harder armored enemies, and thorny briars spawning where you kill enemies. they can be fun but you'll probably want to have a group ready to attempt finishing those as the difficulty becomes extremely high.
They are working on a versus mode. As of the writing of this, only an Alpha has been released. I was not able to play that and do not have any information on that mode. If you like Versus modes, like that in left 4 dead 2, that might be a bonus coming for you.
If you are a streamer, there is another sub mode that allows your viewers to vote on hazards and boons that they want to have happen in your game. It is very easy to use. At the map, just click on the twitch button and enter your twitch name. Just make sure you are host or your host has it turned on too. If a few of you are streaming, as long as the host has it on, if everyone streaming starts twitch mode the chats from each of the streamers will be able to participate in the voting of what happens. The frequency of votes and the speed in which they finish can be adjusted in your option settings.
A few things that may help you starting out...
In the game settings there are quite a few things that are not turned on by default that can help. If you don't want the game to recommend a different hero, you can go into the network settings and tell the game not to recommend other heroes. If you are having trouble keeping track of team members, you can go into the settings and set hero outlines from "on" to "always on." If you would like to have actual numbers on your hud, you can turn on the numerical display. Also, the game has a stamina mechanic. holding block will show you your stamina in the form of shield icons. a normal hit from a normal rat can be blocked for half a shield if you are blocking it from the front in your effective block angle, but you will also block outside of that angle and block behind you as well, it just would cost a full stamina shield to block outside of that effective front angle. Each weapon has a different cone shape for what costs half stamina to block in front of you. if you hover over the melee weapons it will show that cone in the top right corner of the box that appears. You can also push using stamina. this will cost a full stamina shield to do. To push, hold block and tap attack. If you want to deal some damage when pushing, instead of just tapping attack while blocking, long hold your push and you will follow up the push with a melee attack. get used to dodging and blocking as they will become very necessary in the higher difficulties.
The players in this game are usually great to work with. There will be a few bad apples. but try to be friendly and don't hog all of the supplies, and most people will be great to play with. Another small annoyance is if a host leaves, it will end your game in normal co-op campaigns. In chaos wastes it will just kick back to the start of the map you've been playing. if you do get disconnected from a game in the CHAOS WASTES, if you are quick and get back into the same game with the same character with the players you were playing with, all your boons and coins, will be restored to you upon rejoining.
I Hope this helps in your decision to pick up the game, and maybe i'll see you in there! Happy Exterminating!