User blog comment:AP Sejuani/CB1 Xia, the Ancient Darkness/@comment-533780-20150330121256/@comment-24333627-20150331030158

Thanks! You make a good case. I've changed the ult to scale with the total distance, reduced the mark duration, and increased the scaling per 100 units to compensate for the lost 1.5 seconds.

I think this way does work better for an assassin, since it's more of a hit and run kind of thing rather than "look scary and force the carry to run away from you" which, even though it's a bursty ability, might be more fitting on a tank or bruiser who can survive long enough to apply pressure on the carry for the full duration of the ult.