Actual defense options?
Tanks are to most so strong that they might as well be untouchable.
I´ve seen Mundo run over Tryndamere in a fight, building only armor.
Sejuani can with runes, her passive and stoneplate basically reach 7 seconds something of being invincible, Shen can do similar things, at least when dealing with AA heavy champs.
20k+ health cho is not a dream, its a very real nightmare.
Of course, when Riot decided they wanted some options against that the result is that those options usually melt everything else if allowed to do as they please.......idea is that you dont let them do that.
Same goes when dealing with any other carry when they are fed......of course a 3,6,5 wont be able to endure the pressure from a 10,0,0 damage carry, they will just bury anyone not equally fed beneath their gold and add the bounty to the pile.
But then again, if your team feeds the enemy that much chances are its already done and the team has already tilted of the earth.