These abilities are not overpowered, so there is no need to remove or change them.
Comeback kid: After you "comeback" you only have 1hp. Get hit once more and that character is dead. Not fun if your character is poisoned, burning, etc. Helpful in the beginning of the game, practically useless mid to late game.
Leech: If you get hit, then you heal like 15-30 hp. Later in the game that is less than 5% of your HP pool... The talent is certainly helpful at the beginning of the game, but is far from being overpowered, it is actually a completely useless skill later in the game.