In the Legends novel _Shadows of the Empire_, Darth Vader does use Force Healing. In the movie _Empire Strikes Back_, the time you see him with his helmet off-is actually a chamber he uses not only for communication, but also to focus his time into healing the permanent damage. In the SoE book, he uses as much hate as he can, but can only remain outside his breathing apparatus for something like 15 minutes, and it causes him pain to even do the act-using more rage to make himself last longer each time.

It may just be Legends, but it fits into the canon universe.