Rework Conqueror to deal percentage health adaptive damage.

In this video I was Yi with a 4k gold lead on the Tryndamere. I bought a Randuins so I could split against him. I know that on even gold Yi can't deal with Tryndamere, I have no issue with this, most champs can't deal with Yi in a 1 v 1 scenario either. But what blew my mind was how much damage he output with a gunblade, statik shiv and rageblade components. I understand he had a full Fury bar(65% crit chance when with Shiv) and had his conqueror stacked, I got lucky that he failed to ult and diee. But lets notice two other things: he does not use the ad debuff on his W. By this point in the game since Trynd doesn't put points in ult(after 6) he should have had a 60 ad debuff(rank 3 w) which would have shaved some true damage and physical damage I was dealing. Now this guy may have been putting points in his ult, but regardless he simply did not use his debuff(maybe he thinks it just functions as a slow XD). Now I immediately meditate in preparation for his ult. This is a terrible idea against a Tryndamere crossing the 4 item mark(he would beat you to death through meditate even before conqueror.) But here this guy is not at 4 items, hell he's not even at 3, in fact his build is straight up troll: he has a gunblade. 80 AP that only was used once on his E.

And here's my issue. Had this guy ulted he would have beat me to death with these items because of conqueror: a keystone that was meant to counter tanks is instead countering situational defenses such as flat damage reduction. In my opinion it shouldn't do that. If it is an anti tank keystone it should function as antitank. And what better solution than to look to Kogmaw. Make conqueror do percentage health damage(whether onhit or as a spell effect or both and the values does not matter to me, that can be adjusted and balanced. But it would be better versus tanks and worse versus squishies and reduced significantly by damage reduction but not by defenses of health stacking. And to make it harder to itemize against make the type of damage be adaptive to be the opposite of the main damage type of the character using it.

Here's a calculation of how much more damage Tryndamere deals to a rank 5 meditating randuins tabi Yi(I was at rank 3 which is still sizable damage reduction) with than without conqueror: https://www.reddit.com/r/YIMO/comments/8wu1ib/tryndamere_now_deals_271_damage_more_than_he_did/

So what do you guys think? Should conqueror be changed to do percentage health damage or stay as it is right now? Since the new conqueror will add bonus damage it can also not grant AD but also can be now balanced without having to stack it as well.