First off, I love this game. I think you are doing a lot of things right. Some of these suggestions might already be in the works. If so, great.
Show debuffs on mobs. It would be really nice to see what debuffs and how many stacks are on mobs.
Give loot a chance. I know that everything is RNG. I don’t expect to see perfect items very often. But, it would be nice if loot that dropped had affixes that made sense. Maybe more affixes for the class that you are playing and not as many totally random affixes.
Along the same lines, exalted items that have affixes that make sense. I think in all my time playing I have seen 2 or 3.
I love the crafting system. However, either I am the most unlucky person in the world or the % for crafting just aren’t what they say they are. I cannot tell you how frustrating it is to finally find a piece of gear that is usable only to have it fracture with and 80%+ chance to craft successfully and then it fractures. This happens very often. Again, in my case because I can only speak for myself, it seems I fracture Items 80% of the time when as described above it should happen 20% of the time.
Better set items. Most if not all are subpar to say the least. Set items should give you a great advantage and have affixes that make sense. Considering the stats you give up to wear them, this is definitely not the case at least IMHO.
Damage. It would be nice to see your own damage output including DOTs, crits, etc VS damage being done to you and what type of damage. Maybe color coding. For example, darker colors for the damage type being done to you. Red for base damage. Darker red for bleeds, dark green for poison, dark orange for fire, etc.
Placement of buffs debuffs. Instead of putting them down low so you have to look away from your screen to see them, put them on the screen. Maybe buffs in the upper left, debuffs in the upper right for example.
Give us the option to keybind skills to other mouse buttons.
Better unique item appearances. Uniques should each have their own look that corresponds to what the unique item does.
I see that this has been posted already but I think its worth repeating. Show what gear your character actually has on the character screen. It’s cool to look at your character and see the actual gear you have worked hours to grind for, gamble on or craft instead of being generic.
Character customization during creation. This might be a big ask I realize but it would be nice.
Lastly, I just want to reiterate that you are doing a lot of things right. You are well on your way to having the best ARPG out there. Thank you for taking these suggestions into consideration.