This will probably be an unpopular opinion but having now gotten three classes to 25 (Druid, Sorc, Rogue), my biggest take away from this beta was… boredom.
Open world and dungeons play out like this: Run 15-30 seconds, run into a group of 5 enemies, run 15-30 seconds, run into a group of 8 enemies, run 15-30 seconds, oops dead end, backtrack a minute or more with no combat. In the open world, at least you occasionally run across an event to break the monotony, unless someone else is already there and it’s mostly over.
Then there’s the dungeons that play the same every time: Kill everything in small clumps of mobs around the map, open door OR find items/levers, open door, move to next area with the same tile set; repeat until you reach boss room where you get a predictable sub-boss that spams the same set of moves and summons the same blood, spirit, or skeleton adds.
The skill trees are also boring because they’re the typical “increase damage/function by %” crap skills that are difficult to qualify in the gameplay experience and really only benefits people who make spend more time making builds in Excel spreadsheets than actually playing. Adding another x% to my resource pool is an utterly meaningless and unfulfilling “skill” point. It also means that there will be mathematically quantifiable “best/meta builds” that people use to the exclusion of everything else, and if you’re not “meta”, you’ll be on the outside looking in (similar to old end game raiding back in vanilla through WotLK WoW).
Interacting with characters for dialog is a slog. Ask a NPC a question, wait for camera to do a slow zoom, hear dialog, wait for camera to zoom back out before getting the dialog box again to ask another question or progress the quest. So much wasted time on pointless slow zoom animations…
Say what you will about the pitfalls of Diablo 3 but I was never bored. In D4 Beta I was continually bored by the lack of action, the lack of enemy and dungeon diversity, and the really slow NPC interactions.