Just as an aside, I don't think that it is a big deal to have unkillable epic characters. The Dark Wanderer epic destiny, for example, literally makes a PC totally unkillable. No matter how they die, they show up 12 hours later with all their possessions in a location of the player's choosing.
Many Epic Destinies make death unlikely or a speedbump. Heck Undying Warrior makes dying highly unlikely at 21st level (1 healing surge brings you up to bloodied value) and it is just about impossible by 30th.
The whole point of Epic Destinies seem to be that you have bigger things to worry about than your own death.
As to the OP, I think I certainly need to see it in play before announcing broken.