Hello,
There is a bug with umbral blade in online that makes the aiming of the skill very innacurate and damages the gameplay experience heavily.
In addition to not being accurate, you can see in the video that the animation between online and offline is different: in offline the animation is smooth, but in online, the blade disappears before arriving and turning into a blade vortex.
Here is the video i made to demonstrate this : umbal blade throw online vs offline - YouTube
Thank you