It's worse than you thought: The mutation status will copy the previous creature's full attack and HP and add 0-4 to each, and set the current attack and HP to full. So, even if the original dragon was damaged and Antimattered, the copies would still have full attack and HP.
That said-it is not something you can strongly control through deck design, so I don't consider it OP. It is similar to Dusk Shield blocking all the hard-hitters attacks.
If zanz wanted luck to have less effect on the game it would be changed, but its power level should not be the reason to change it, because it is so inconsistent.