Riot Games confirmed that the hero s visual appearance and abilities have been changed a bit. However, the most notable change in Dr. Mundo is his passive skill, which prevents enemy heroes stuns, slows, and other immobilizing effects.
Since this is a major change, some players will make their own metas using Dr. Mundo. As of the moment, he is considered a bruiser tank. He is usually played as a bully tank top-laner or a super-tank jungler.
But, he could now be used in the mid lane, thanks to his passive. Take note, most of the mid-laners in the Summoner s Rift are mages, which means that they rely on their skills to clear minion waves and poke enemy heroes.