Campaign map interface is terrible.

And I have no idea how you managed to mess up something so simple.
Maps (especially the ones without linear progression, so acts 2 and 4 for now) are hard to navigate around. They aren't too big or too complex, but somehow still hard to read (and the fact that you shuffle all locations every league only makes it worse). PoI icons are hard to see. And tracking your skillpoints and various permanent bonuses that you supposed to gather through the campaign is a nightmare. I feel like I'm fighting with that GUI every time I have to use it.

Atlas interface is in a very bad shape as well, but that's another story (although I assume that the same person is responsible for it).