Would like to see two things changed with fast healing (FH).
1) Have FH spread out as more past-lives are added. Example: Rank-1, tick every 60 seconds. Rank-2, tick every 30 seconds. Rank-3, tick every 20 seconds. End result, same amount of healing but spread out, rather than all at once.
2) Allow FH to resist / ignore the Reaper self-healing penalties as after all this is an Epic past life ability.
Edit: To add to the list, allow for temp hitpoints if the player is already at max hitpoints.