Agree with all the list here - UI/UX and movement system probably being #1.
Another thing I'm hoping they bring in earlier than later in the EA would be the Mercenaries system (even if roughly at first).
I like the companions quite enough, but since we're replaying everything with each patch, it'll be really great to just be able to go with Mercs and use party compositions we haven't been able to yet.
I.e. next patch I would love to run a Moon Druid + Dragon Sorc + New Class + Ranger party. Just something different.
