Genetic disorders that you seem to be talking about are things like heart valves formed incorrectly. if it brakes something critical you die, if it breaks other stuff you have whatever problems from that. thats not a replication error, thats a blueprint error.
That's an excellent way to put it: yes, I was referring more to the "Bad BluePrint" type of Genetic Disorders, rather than the "replication errors" like cancer which I think the Magical Component of Wizard Healing is fixing (ie. it always Heals back to perfect rather than giving up early or getting it wrong part way through. In other words I think Wizards are all but immune to your standard cancers, or anything that is related to Accumulated Damage, which would be prevented as part of the No Scars thing.