I agree, England by far looked like the better team, so I don't think anyone would argue that the decision probably affected the final outcome. I do agree that red cards do kill the contest, especially when a team receives one early in the game. At the end of the day Rugby like all professional sport is in the entertainment business and I'm not sure red cards are adding to the spectacle in a positive way.
My only concern with the 10mins off and then you can replace with another player option is, what stops the team in say a crucial game having a player take out a key player in the other team, they play 14 and then sub on a better player off the bench. I'd like to think no player or coach would sink so low, but the punishment might not be correct for the impact on the team who have now lost their star player if this scenario occur (premeditated or not).