Tanks need less damage

I recently just got back into the game, so im a little bit rusty, and I played vayne/blitz vs leona/taric bot. They both bought relic shield so that they could just give eachother free gold, and taric was the adc. For me, it started off really well, I got 3 kills and an assist in the first 5 minutes and was poppin off and we were winning lane by a large margin. At one point, leona hooks me and stuns me, I didnt really care because I didnt think they'd even get close to killing me, taric (since they are connected with his W) stuns me as well while i was still stunned, again I didnt think they'd hurt; they then proceeded to almost oneshot me, if I hadn't healed and flashed out. Keep in mind, at this point, Taric had Phage and leona built some armor and they both had relic shield. Leona had aftershock, which did a pretty big fucking chunk of damage. my team also underestimated their damage output and died as well, whic let taric catch up to me a bit. At that point, me and my blitz tried to shut him down, so we caught him out in a really crowded spot that was, granted, not the best idea to fight him, because he stunned me and used his lethal tempo to kill me before i could even leave the stun. He only had Phage and Sheen at that point, while I had a full Statik Shiv and boots_(a mistake to buy vs 2 tanks-i know) _, I did misplay a bit but he still killed me before i could even fight back. Eventually there was a point where his autos did 1/5 my HP every hit, but by then he was super fed because leona would EQ then he'd E with his W and kill you before you could even react.

The only reason they even got that fed was because they could burst you down so easily while you couldn't do jack shit. Kiting them was difficult because Leona could R or E and Taric could E-Flash and once you got caught in either, there was no escape. Again I probably played terribly, but I know that taric shouldn't be able to kill me so easily just because he has a fucking Lethal Tempo. And he was also too hard to kill for the rest of my team because he had so much god damn HP!!

If tanks are tanky and can CC the shit out of people, they shouldn't be able to do so much damage, whether it's base damage or scaling. A tank should be allowed to buy whatever damage items they need but shouldn't still be tanky while they're at it. If you want to go Leona/AD taric, be my guest, but you shouldn't have almost 3k HP while you're building full damage and the "tank" leona shouldnt be able to hurt me while she's building full tank. I know I played that terribly, I'm rusty as hell, but I also know that kind of bullshit shouldn't be allowed in this game.

TL;DR: Tanks need to lose their damage

EDIT: I just want to clarify that my own problem wasn't killing them, that was my team's, my problem was how easily they could kill me