Nerf sustain already.
It's not even about
, Just champions who are squishy have enourmous sustain right now, and they are unkilable, mainly because they nuke u first. U can't really counter it with hp, only with other nuke and cc. In runes there is conqueror, taste of blood, ravenous hunter, bloodline.
Items

Bt empowers Draven early too much, he is a terror to lane against, with normal adc, u can just start fight him in the mid game unless he didn't stomp u, other carries buy it later maybe as 4 or 5th item.
Death dance makes riven and few other champions just kinda tanky, + they got high sustain, oh and sometimes katarinas buys it because its better defensive item than 300 hp with 80 ap item.
Gunblade makes kata broken, just a perfect synergy item, but her heal with conqueror ravenous hunter and gunblade make her almost invicible in teamfights, She is just healing half of her hp with one jump into the teamfight, and is nuking your whole team. No one is buying this item except her and akali. Akali wouldn't even mind if she would just loose some sustain, she is not that much oriented on sustain but katarina maybe would just start buying HP items, instead of healing shit tons of hp, with 0 hp items being able to survive 5v1 engage with just sustain.
Wits end makes mages useless, most of mages have shit early and mid game, while any aa dependant champion can just rush it first or second item and deal with them easy. + new passive is just perfect synergy for master yi, which was kinda countered by mages in mid game, now he don't have this weakness. He just buy mercs, wits end and says goodbye to mages who tries to stop him from 1v5.
Just most broken champions who are using these items are: God tier for these items

second tier

. They are not some rare seen champions, I meet them almost in every game.
Im not saying to nerf these champions, but nerf sustain overall, from runes and items. they are healing way too much right now, which makes them too much safe. Grevious wounds feels useless right now, no matter what u buy, even if it cuts 50% of heal they still heal shit tons of hp. They would have to reduce heal to 75% already to being able to stop sustain in some way, but It's bullshit to buff grevious wounds that much, just nerf sustain so u even won't have to always rush these items.