Why is %current health damage used?
Originally Posted by Riot (View Original Source)
We put % current health damage on spells when we want those abilities' effectiveness to be independent of how much health the target has or hasn't stacked and:
The spell's intended to be used early in a fight as a core part of the champion's play pattern. Xin Zhao's ult is a great example of that - % current health damage reinforces the message that the Armor/MR bonus already sends, rewards using the ult to make big early plays that split teams.