You know, it's one of those things where what you think you want and what you actually enjoy might be different, so I can't 100% say "make this game this way and it would be perfect". But I do think I have a good handle on what I don't like.
Combat is too hectic and RNG dominated. I don't mean that the actual damage you take is dominated by RNG, but rather the combination of monsters you face is like a giant RNG slot machine and certain combinations just do absurd damage while other combinations are completely trivial.
Breeches, for example, some I'd have no problem at all and I'd be struggling to find more breech mobs to kill because they die so easily so fast. Others are the opposite, taking multiple hits just to down one mob and they spawn out of control filling the entire screen rather instantly. In a more strategic game, I'd look at the mods of the mobs and figure out why I'm having trouble with one breech and not the other kind, but again going to my "hectic combat" complaint you don't even have a fraction of a second to do that before you will die.
Honestly, I think the biggest problem is alt-f4 (or using menu to quit) & town portals refilling all flasks life and mana. The game literally gives you a full heal + all resource heal for essentially zero cost, usable in an instant. It also gives you an instantaneous get out of jail free button. So the developers have to balance around these things- nothing that kills you slow will EVER be a challenge when you can just use a TP to full heal. Maps put a limit on portals, but a lot of game time is spent before you even reach maps. Make it so you can't use scrolls in combat, and alt-f4 just disconnects your client while leaving your character in game for 10 seconds. Balance around THAT. Then the game combat could be made a little bit slower and more strategic, and not rely on RNG burst.