That is just matter of taste ...
Personaly i dislike those empty unuseable space ...
I would say of one looks a game and concludes that places not covered by UI are unusable spaces then it's quite a failure of the game! One would hope that the UI would be covering the game space, not be it.
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I even let it auto fill, which is something I wasn't going to do because I hated it on the old hot bar.
I do to, but that's mostly because I don't use much hotbar.
Items being separate from skills already helps a lot. I think that if they improve organisations to automatically generated decks, and make hotbar act like hotbar, and remember what was and wasn't put on it, then it will be alright, even of rather overengineered.
I think we can now move on and focus on complaining about minimap and combat log
