One of the simplest things they absolutely need to do is have a mini map indicator for uniques and set items. I almost missed 2 of them while playing in the beta. Also an option to auto drink HP/Mana potions as you pass over when your belt is full (and hp/mana is not full) and being able to quickly fill the belt from the potions your inventory all at once.
It would not change the game in any way and feels needed, also controller support on PC causes massive camera stuttering but that is something I brought to their attention as well.
Anyone else have more QoL they would like?