Defensive items on TFT are better then they are on SR
In the last game of TFT I played, one player got a pretty early (round 7) 3 star 
He then put Dragons Claw (83% MR)
(immune to crits) and
(infinite scaling AS)
So the Kass was almost immune to magic damage, immune to crits, and his attacks grant him a shield, and his attacks get faster the longer the game goes
When that game of TFT ended, the Kass player was still at 100 hp because Kass couldnt be killed
Meanwhile in SR I have 150+ MR and 250+ armor, and still die in less then 3 seconds