Twin Enso, Riot's game designer for League of Legends, made an announcement of the upcoming changes to one of the champions, Dr. Mundo, who will get a rework in the future. This one "will make him nearly unkillable", as per the developer's comment. This refers to the late game play. In the current patch the champion has obstacles to scale better in later stage.
Dr. Mundo's vulnerability has a couple of points to take out. He is dependent on basic stats. Previously teams were using him as a tank. In Enso's words, Riot wants to see the champion in a proper use for late game, as for now he's really dependant on a good start and early game dominance.
The exact time of Dr. Mundo getting his balance is not announced yet, but the community believes it will already be buffed with the arrival of the 12.5 patch. This one is scheduled for March 1.