Class design mostly, everything feels slow and clunky. It's never nice to have abilities and spells taken away, or baked into talents, and then have talents taken away after that. There's a famous quote where I think Ion goes on about WoW not being a "twitch shooter", which I think is an ideology that permeates through BFA. Prune, prune, and prune some more. I've never known downtime to be as bad as it is currently, especially for melee specs, and if it's not, say Fury Warrior? You're sat there spinning around in circles in between, hitting like a wet noodle.