The Very Fast Healer and Regeneration mutations do not function as you might expect, and IMO they are very weak. My first issue is that the swift sleeping regeneration provided by Fast Healer is not preserved by the later mutations; if you have Fast Healer you can regenerate almost any wound in about ten hours, but if you get Very Fast Healer, your sleeping regeneration drops to ~30 HP in ten hours’ sleep.
My second, lesser concern is that the regeneration rate of Very Fast Healer/Regeneration is very slow; you get a 20/50% chance of regenerating 1 HP every 30 minutes, so Regeneration only heals ~1 HP an hour. This could probably be stand to be increased; as it is, neither has much impact.
Fast Healer itself probably does not need any changes.