Mundo. Why damage doesn't matter

Mundo is a pain in the neck, i've been in and watch many matchs now with mundo as a champion in the game. All of them have seen him with tiny amounts of deaths normally from the early game, then him just not dying. I think it is insanely dumb that there is a champion who can take turret damage and three champions all hitting him at once without any problem, even without hit ult his strenght is insane. Due to his insane surviablity they rarely ever build damage yet even full tank they can just kill anything due to just out lasting all the damage the enemy can throw at him. In my last game we threw a team at him including three ults and he came out of it with more health then when he went in with his ult. This is insane that it in the game, he need a nerf even the enemy team was saying so. When mundo is in a game there is no point playing for no matter how far ahead you are or how well your lane did, mundo still will not dying giving the enemy a tank and a pusher who can just keep going without fear. His Q maybe have a stacking longer cooldown so each time he uses it take a little longer to use the next one, not changing it massively but stoping the perma slow and range damage he brings maybe but that a small problem when you look at the bigger problems.