Yea, tier 4 carrys are just a bit overtuned, most games the top 3 are a random bunch of frontline and CC with either drave, jinx or akali on fullgear, and the worst thing is that jinx doesn't even have atleast one other gunslinger, she can work out completely solo, same with akali...
Their interaction with certain items(BT on vraven, giantslayer jinx or IE on akali) are just to poverfull.
And if they are smart, they have tow dps items and either trapclaw or dragonclow so the few actuall backline threats like vi won't be an issue anymore aswell...
And yes, general tankiness is mostly like on the rift, once the carries get some gear it just doesn't matter, mr and armor are just pointless.
Dragonclaw is strong cause 75% reduction in addition to mr, Iceborn give dodge and as slow on top of armor, warmongs has huge sustain, PD critimmunity.
But don't make the mistake to think that items like redbuff or thornmail actually help getting tanky, cause raw stats do next to nothing.