My personal 3 most wanted QoL improvements as suggestions:

[unique iron]

1. Fast forewind speed options in any dungeon or boss fight; permanent multiplicative challenge tickets (waiting for 20x goblin lair or any other dungeon completion on a daily grind basis is pointless and doesn't contribute to any progress)
2. Multi-item-sell option; filters should remain active during selling process (after selling one piece the filters seem to remain active; however instead all item sets are displayed until re-selecting the item filter - for example affinity/type)
3. Too many clicks and view changes in the hero menu - hero improvements and gear changes and leveling should be in one carefully designed UI window, all options easily accessible

Kind regards to all

Edit: Improved description of point 2.