Nah, Shock is great. There's a reason Retainer is regarded as one of the best Rages in the game; it's a quick source of damage to all opponents and if he gets levelled up enough can steamroll any set of opponents in one turn regardless of their strength. As for the Offering having less damage per hit, when he hits the damage cap that doesn't matter so much since he'll be able to do four hits of 9,999 damage rather than one. Even before he hits the damage cap that still means he's dealing twice as much damage per round as he would be without the Offering.