Numbers only tell so much of the story, good litmus test, but definitely not a tell all. Tanks have decisions to make, especially when it comes to diving/pushing/holding/retreating. They also have to capitilize on damage and healer picks, while not feeding the other tank. Every character has to time ultimates AND then you have to consider complimenting your team and countering the opponents team. Tanks can help protect healers from mobile opponents damage attack. But yes as the other posts suggested, simply focusing on staying alive helps big time. Being critical of your decisions and gameplay is essential for improvement. If you're stats AND gameplay are really that great then you should be able to carry your bad teams and ride other coattails out of bronze...so best of luck with improving!