Through HCI & visual eye tracking it's been discovered that when people load a webpage of text, their eyes briefly fixate at the top left. Researchers basically all agree the reason we do this is because we have been trained to expect the most useful information (for this time period) to be there. In this 'battleview' thing that PGL have made, it's moved really far away from what Dota players have been trained to do in a teamfight. The biggest problem I noticed was when I was watching a team fight, there are a few points of information I need, and they are no longer in their expected place. If I want to see who's dead, I automatically look for the hero icon at the top of the screen. That is blocked by this overall player health stat. (Which is such a generalisation of a team fight I'm not even sure how exciting/relevant/interesting it is) You cited about wanting to know which heroes have used items, such as BKBs. The BKB design itself is made to be super obvious when a hero uses it, because it's arguably the most important team-fight item. Heroes turn bright yellow and grow, it's not hard to miss. In fact, all items and abilities in dota have been designed with this in mind, therefore we as spectators and players, have been trained to look for these. To get information about what items are being used, we look at the actual fight. Dota Cinema does this really well in their plays/fails videos. If we need to see a specific item being used, they put the icon above the hero using it - where we are trained to look. Now, this is probably impossible in a live game, and would look way to cluttered if we did it for every item, so, how can we only show the specific items that are interesting? This is why we have casters. In a team fight, we're sort of doing visual search between all the different aspects of a fight. Humans are really good at picking up colour (The Williams test, 1966). This is why valve grey out heroes that are dead, and we have those little banners that are gold tinted if they have buyback. Super important information at a glance. The health bars in the PGL 'battleview' don't have any of this. They go from green/grey to just grey. A hero on 10%hp looks super similar to a hero on 0% at a glance, which is all we have time for during a team fight. tl;dr, I'm rambling and this is poorly wrote - but this GUI is a nice idea, but it doesn't build on what we know, it's moving away from what Valve has trained us to do, and what we are interested about in a fight. If you really want to make a good gui for this, get some eye tracking software and see where spectators look in a fight, find out what information is actually missed, and put that information where they make inefficient observations. Data driven design is fun.

Also, the minimap is hidden. HUGE mistake, pretty sure eye tracking of dota games has shown this to be the most important part of the UI.