Can things get any worse

Main question is: DOES TANKS HAVE SUSTAIN IN MID/LATE GAME ??? My thought's are :

1. MID- they have more like 50-50 chance to do something because enemy ADC don't rush armor shred and lethality items.
2. LATE- probably "they never have a chance". Reason is that most ADC have already have at least one items that goes through armor . My biggest concerns are why are tank like underdogs in the games. I am talking about true tanks not DMG sustain tanks. I am talking about pure armor/magic resist items( maybe some CD and HP). Tank: -armor -magic resist -HP -CD ADC: -lethality -armor pen -magic pen -true dmg -percent max/current HP -crit

• currently there is no counter to CD otherwise LoL will be like no reason to play tank when you can play fighter or some burst DMG champ. And I want your opinion on one shot/5 sec kills system. I think it looks great but when a champ have huge amount of HP and come someone that kills you in less then 5 sec it Hurt's. You build everything to counter him and he kills you anyway. I am Sion main and I have really hard time playing full tank. My friends remember my plays in the old days( everyone says I was a monster at tanking, they mean even when we lost the game I was the one last standing and enemy team needed like 2-5 minutes to kill me).I wasn't angry because we lost then, but when comes a champ from jg or mid with half items and kills you in 5 sec it hurts really bad. Despite being a shield for my team I die in matter of sec with full armor/ magic resist build and resolve runes. I need some advise from you guys. And pls don't tell me to play other champs or play tank champs like they are fighters because THEY ARE NOT FIGHTERS THEY ARE TANKS.