This game sync the player's position on the server side, every 0.3s, while other MMOs do that on client side, which is instantly. A simple test, try casting something while running in town & see how long it takes for the skill to get interrupted, try that again in other games. I'm playing ARR at 70ms with battleping, & it still takes ~1.20s to interrupt the skill, while in other games it cancels almost immediately even at 200-300ms...

It's bad netcode, not entirely player's connection... And those 2 things do add up