ARURF is a proof that tanks deal too much damage
If you have played ARURF you couldn't have not got One-Shot by Malphite or Garen with pressing just 1 Button, or champions like Poppy hitting you with E 3 times and 2-3 times with Q to kill you for 4-5 seconds while building full tank and having 4000+ HP with 300MR and 200ARMOR, Some of the champions in the tank class have way too high base damage ( Poppy ) or high ratios ( Garen, Malphite ) It is impossible to kill Poppy but It is also inevitable not to die from her unless you flash away but who told you she doesn't have flash as well, also cool thing I've learned today you can use your E with Poppy while rooted from abilities like Jinx's E's, so CC can't counter you too...
Overall most of the tanks deal high damage when building tank and there are those tanks that build AP or AD and One-Shot everyone around...
At least there are some good tanks that are not supposedly broken like

