I know I'm going to get a lot a flack for this comment, but Mundo is horrible in the new Shadow Isles Twisted Treeline(SITT). I've played as him and against him. So i know what im talking about. When I see him on the enemy team I say, "sweet. We got this".
Ignite wrecks Mundo and everyone takes ignite in 3v3. The hatchet makes matters worse.
I challenge someone to make a video and post it showing How to play Mundo in SITT. And I don't mean post a video of a fed Mundo. Any champ is op when fed. I want to see actual skillful gameplay with him.
So.. we went 15/0 straight to diamond with a Mudno+Karma comp on the new map.
Mundo is strong when your team follows up on your plays. It's all about trust. The best 3s teams don't necessarily consist of high elo players, but players with decent fight mechanics who follow up on eachothers plays constantly.