Riot, leave the Sejuani's E base damage and CD as it is.

By changing this, you are making more tank oriented than ap burst. And yes, I prefer much more to play Sejuani as a AP "assassin" than as a tank. Leave the CD and damage as it is or make it a flat 9 sec CD if you really want to buff it's CD, but make the damage stay or increase the AP ratio. I really love to play her full AP instead of tank