If you mean heroics, I could AoE tank a lot of heroics when I had equal stats as you.
If you mean in raids, then warrior/druid/paladin mitigation is about equal, DK tanks are overpowered in a lot of situations(council/chimae/conclave/countlessotherexamples) but we're all used to it by now anyway.
Are you using your cooldowns properly? is your healer actually healing properly? Are the healers priests?