Make his passive show how much XP he will give to each available target.
Right now it just shows a yellow line if a target is able to be leveled up, but it would be nice if you could see exactly how much XP you will be granting. If there are multiple targets, you might want to give a level to the person who will gain the most XP from it. Maybe you'd want to save your passive if someone is only ~20 XP from leveling up for a later time when someone else is ~200 XP from leveling up.
Even just having it show a little number above the person if you hover over them would be helpful.