Do you heroic strike on cooldown? Has Inner Rage a 50% uptime? Your other tank got your vigilance? If your answer is three times yes and you hit your buttons as "hard" as possible there's not much more you can do, a log might help.
Every 1k dps you contribute more to your raid that's 1k less your dps has to bring. Aggro is not an issue with 500% buff, it's your raid's dps that needs a bump. Both of your numbers sound rather low but there isn't anyone ranked much higher on the blocktank side just yet.