In comparison to glaring gameplay issues, this may seem trivial, however, I truly believe this bug risks ruining immersion for many players. I know it does for me, my friends and many of my guildmates over the years.
Ever since Mists of Pandaria and the introduction of the Cloud Serpent model; I have noticed that when on certain mounts the player character scales (usually shrinks) to appropriately fit the mount, instead of the mount scaling to fit the player. The linked video shows just a few examples. I find the Shadowbarb Drone to be the worst on the list so far.
Again, I know this may seem trivial to those that play this game as though it’s a mathematical equation, however, to those of us that like to feel immersed in our characters and the game world, bugs like this that go on ignored are a real nuisance.