Why damage items dont work on kayn

damage items like duskblade and crit items don't effect kayns damage like it does for zed. I got fukin deleted in three hits against zed with crit items on. he only had one item which was infinite edge and three shoted me. kayn is a burst champ just like assassins but he cant trade worth shitt. also as rhasst you guys fuked up his heal bc he don't do spell damage yet it heals off that. for his ult it should heal him like a vampire but not goin off how much health the enemy has. yu shoud be able to heal a lot off all champs n not just tanks. the ult would make yu better to outplay by sustaining. the reason I say this is bc after yu use shadow step yu cant excape so yu would have to rely on auto attacks and yur Q just like Xin and his E. plz make changes bc I also got raped by trynd and he only had static shiv. trynd is strong just with one damage item n is a pain in the ass and gots a ult that just makes him sustain so if yu manage to get him b4 yu he can still just own yu. kayn wont be op with these changes he would actually be a great counter for some of the champs that people still think are bs like trynd also with ult being changed this way yu would be able to pull off great triples, quads, and pentas. it wouldn't be ez bc yu still would have to have a strategy on who yu want to ult to pull off a trip quad or whatever. Plz take this into consideration and make changes thx.