1. You have to hold your mouse perfectly still for a moment before right-clicking an item to deposit, withdraw. or sell it. Otherwise, it thinks you want to move it. That's sort of brain-dead because I would use left-click to move things. At least give the user a 10 pixel in any direction grace area around the click before you consider it to be a move.
2. As a compulsive looter, not being able to effectively loot and vend the items in the Expeditions (at my level) is quite annoying. Yes, I can go back through an entire zone and pick up all the white and blue items that I skipped over because I don't have the inventory to carry it all, but that would take a load more work. It would be easier if I could just teleport to town and vend it like with Mandates. It's not like there's a timer on the thing. Even in D3, you can port back to town in regular Rifts, which also drop loot everywhere. You should always be able to port back to town, no matter what you are doing.
3. Now that I am thinking about it, having to hunt down a boss is tedious. Sometimes I am all the way across a zone and now I have to travel all the way to some remote location that explored a while back. The retread is a waste of my time. The boss should not be spawning in a set location, but in a suitable, large enough spot nearer the player.
4. Please, please, please, do not show any part of the map that I have not yet visited. I often get very confused about where I have been and where I have not. The discovery radius should be no larger than what the character can see on the screen at the moment. As someone who enjoys exploring all the nooks and crannies of a zone, this is tedious.

EDIT: Sorry, this is number five... please give me a way to make my mouse cursor more visible. I often lose it amidst the chaos of fights and end off going in some weird direction I did not intend. A larger, glowing cursor option would be ideal.