right now, all he needs is improvements to the a.i. of the villain mechanic.
the most important part is, that it actually lands on the largest carry threat on the enemy team, instead of the enemy support or just someone who happened to pick up a kill or two by coincidence or cleaned up a fight while another enemy dealt all the damage.
the reason why the initial damage reduction on his w only lasts for 0.75 seconds is so it rewards proper reaction time. its basically like a fiora parry. if you wanted to buff that part of his kit it would make more sense to buff the strength of the effect instead of the duration.