Just doing some simple testing.
The moment you hit a mob, you get slight delays
It’s enough to reduce your number of auto attacks from about 19-20 every 10 seconds down to 15-16. Or a 20-25% decrease.
Autoattacks (and all skills, really) are tied to your server ping. You tell the server you hit something and start the animation, then the server tells you back that you hit something, then your client finishes the attack animation.
If you have a big ping and fast attack speed you might see the animation get a bit weird as the ping time takes up more of the animation than the smoothing can handle.