Tahm just pretty much 1v4'd my team

I wasn't around at first, and mind you, he was pretty fed but honestly I was Yasuo (yes, the op asshole everyone hates) and I could barely kill him at the time when I did make my way down there (was only one really doing ok on my team that match). I definitely had to ult. Even without him being fed, he was a nuisance..why is he still allowed to be that tanky and even rewarded heavily for building tankier?