The question is: Do you look purely at damage taken or do you look at Healing Required? This is the amount of healing other people healed you for, so it is basicly damage taken - self-healing done.
This should roughly be the same for tanks in equal gear in the same situation, if not, you need to start analyzing what kind of damage you're taking in more, and how you can prevent that. Maybe you're using barrioer too often instead of SB, maybe the other way around? Maybe you jsut need more hit/exp to get your rage generation up? These are all questions you should be trying to answer when alanyzing performance.