I love class systems, building my character however I want, being able to synergize several effects into one devastating result, and having this all in action game system. Well... be careful for what you wish for.

Ok ok, it's not as bad as that comment may imply. This game is... Diablo. It's a isometric action RPG with random loot drops, tens of hundreds of hours of increasing difficulties to allow for stronger loot to appear, facing against hundreds of enemies a minute (I got an achievement for killing 25,000 enemies, it's that crazy), as well having four-player co-op. Hell it even shares a designer who actually worked on Diablo itself. This whole game, as well as its expansions, were created by a relatively small team, about 13 people or so. That's honestly really impressive considering how content filled this game is.
You have six classes in the base game, and three more added with DLC. Unlike in Diablo (as far as I'm aware, I've not played them) you can multiclass once you reach level 10. That doesn't take long to reach, and when that happens your options get borderline overwhelming. Each class is distinct enough from one another, and with how earning class skills works in Grim Dawn you need to carefully distribute points earned from leveling up. So maybe you only want the second class for a few specific skills and stat ups, or maybe you'd rather distribute points more evenly. Do you want a lot of different types of skills, or only have a select few but invest more points in the existing ones to make them stronger? But you also have attribute points to distribute which gives basic stat ups to your character, however higher level equipment is locked via attribute stats. You could simply increase that stats you need, but perhaps your armor will make the difference depending on the random modifiers they have. Is your armor not enough? Then add components to them which gives small bonuses including brand new skills exclusive to equipment and added components only. Still not enough?! Find and restore devotion shrines to add points into one massive, yet open ended skill tree that, yet again, can earn you exclusive abilities and stat ups.
This is why I said "...be careful for what you wish for". It is so much to take in, not helping how one piece of equipment can have a laundry list of modifiers. It can be difficult comparing different types of equipment to the point that they have an in-game search system where, say, you want more fire damage equipped; so simply type in "fire" and it'll narrow down the list. It's a really helpful tool, but you're still doing a lot of comparing since it may have more fire damage, but it has less armor or maybe your helmet you have on now gives you a fireball spell. There's so much time spend on menus, doubly so if you're as compulsive as I am when it comes to wanting to do as much damage as possible but then "Oh this benefits my lightning spell but now my chaos attack is weaker. Oh god what do I do?"
What you do is say "fuck it". You got to fight the urge to be as perfectly optimized as possible. It's a game based on randomness, at least in terms of equipment. The challenges aren't designed around one build, it's designed for every build. I started to relax more when I came to grips with that. Maybe I'd have an easier time if I continued to pay stricter attention to what I was wearing, but veteran difficulty is perfectly fine with a "good enough" attitude. I then came to realize something else about Grim Dawn, it is a fantastic "podcast game". The act of fighting is simple, but you won't make it far if you aren't moving your character out of harms way. You have to do just enough maneuvering that it isn't a mindless game, but it's no fighting game that requires your undivided attention. It became nice to wind down with Grim Dawn after work while listening to a video in the background.
To go into some of my last scattered thoughts on this game: it actually doesn't do random dungeons for the most part. At least for its main campaign. It came as a surprise since I've heard that random dungeons is a staple for the Diablo franchise. I'm honestly unsure if that's a point in Grim Dawn's favor or not. In case you were curious, I rocked a dual pistol build where my character was upgrading their shooting skills till it got to the point that every shot had, like, five separate 15% to 60% chances of a different effect occurring ranging from lighting to knockdowns to splitting into fragments to piercing straight through enemies. Sometimes they happen all at once. And lastly, don't be like me and not knowing that there's a storage area where you can have a universal box that is shared by all your characters. This helps a lot when making a new character as you can provide some starter gear, maybe give them components or materials, or maybe you found rifle that is useless for your solider but your demolitionist would more then appreciate it.

So to summarize: it sure is a loot-based RPG. I'm definitely more of a Monster Hunter person when it comes to how to create a compelling loot system while not going too crazy with a shopping list of modifiers. Then again, I can't create a army of skeletons, rotting flesh golems and demons in Monster Hunter now can I