Due to the upscaling on Gnome’s size (devs decided they were too small), their mounts are also scaled up.
Their speed looks slower because of this, but more jarringly, the sound is mismatched. The “clop clop clop” is the speed of an unscaled mount, and much faster than the slower animation of the scaled up mount.
On Hallow’s End I put on a costume and once the scaling effecy was removed, everything was perfect. On slower mounts this isn’t as bad, but on the epic it is quite noticeable and jarring.
I have only tested the warlock mount, but presumably all horses, etc. also have this problem.
Solutions: Remove scaling effect on gnome’s mounts, or remove the scaling effect on gnomes altogether.