1) The name of the player above his hero character is a bit hard to read in my opinion
2) You character is hard to see notice in some situations, like in a middle of a fight; maybe adding a circle around your character ?
3) The lower left part of the HUD could have been more efficiently designed; it's kinda big (you might say lower the scale of the HUD, but that would make things harder to spot)
4) The score board from DotA's the upper right corner was pretty nice, where you could see all the players' heroes, level, and other info
5) End game chat