I do think that Sith Healing arts are similar to the Jedi Healing Arts. Due to the dark side energy, Dark side energy can twist the wounds to more grotesque while healing the flesh.
While the Sith Healing Arts heals you, the dark side makes you an ugly little ****. That is why Sidious, Vader and Sion are quite ugly due to their injuries and dark side energy.
Because Dooku, Traya, Caedus, and Revan don't have DS ugliness like those three Sith Lord. It is debatable that Revan and Traya suffer from DS Ugliness or not.
Traya is just old so very old. Revan is just creepy when Dark sided.
I do think that DS creepiness and DS ugliness are different.
DS creepiness would just creep the hell out of you. DS ugliness have scars all over their bodies and dark side energy warps the appearance to the point passed just DS creepy.