Am i being trolled by Kayn or is there a problem? Does he need 1AD more?

Jungle main who mainly plays assassins, so i pretty much know the fundamental system of how much health is a threshold for an assassin kill, certainly at early game. Though it came happen, players getting away with literal shreds of single digit health happen but out of the many many games i have played over this year, i have seen no more than 1% of these occur outside of my 20 odd Kayn games.

I have argued over the time Kayn has come out that his early game damage is !ATROCIOUS!, i mean its fucking TERRIBLEEEEEE. Which is somewhat bemusing when compared to the fact that his jungle clear is actually very good. So what's going on? I've seen, and played cases of Kayn mainly getting fed due to essentially stealing kills by last hitting from the bot lane, enough to only go straight for Rhaast, essentially because of his health, CC and his ult that does, ironically, hp based damage instead of flat.

Is this an assassin or the definition of a broken champion? I'm really quite very very bored and aggravated that i do such minimal and rather questionable damage that ive seen more players get away with aforementioned single digit health, only for then forcing me to play Rhaast (which honestly, i prefer SA Kayns fluid assassin playstyle) simply because his damage is genuinely that garbage that i'm not even playing his as a damage dealer but more just a pain in the ass knock up bot. How can this be intended? Further more; i have had some games with SA Kayn due to the enemy not living on 5 hp, and getting to a point were i'm actually 1 shotting people before they have time to realise they're playing League. What is that ramp up and where? WHY? Items?!

What it boils down to is.. A kill stealer with no real damage going into either a knock up healing bot with a HP based ult or a pure item stat check.

He's such a great champion design wise and i enjoy his kit... His early AD needs fixing, his scaling needs to be less reliant on items and for the love of satan's cat, the stigma of 'i ban kayn because knock up' needs to dissolve.