I really think that "History" part of the Unit or Champions screen should be hidden under another tab. Maybe spells too. It would give you more space to nicely show stats and perks which are on the character portrait and also seperate them in different manner. Story is nice, But I do not think it has to be showed all the time. As Stats, spells etc are more important for actual gameplay.
Also, some simple use of colors in UI would help a lot. Blue, red, yellow would help to get info faster.
My biggest gripe, and its been there since WOM, are those small tiny, arrow buttons...You made great new UI, with huge buttons which are great to see and easy to click at. But you left this tiny pidi mini buttons there....Its not only hard to click on them, but also, I really do not want to click thru all the options to see what is next, like 20times... You could get rid of them completely and by simply clicking on icon make a list to pop up and then be able to mouse over or choose whatever you want.
Other then that, I really like what I see and I hope you will not rush it again and take your time to get this game right. Good luck to you
Ohh yeah, and those big armies on maps full of units looks bad . You should abstract it a bit, like show only 3 or 4 strongest units in a pack or so, and not with all the units, but just one...more info on mouse over or mouse click.