Don't go chasing stats, they are mostly meaningless. It's easy to top damage as any hero if you're against a Reinhardt. Same as when a Reinhardt has silly damage blocked, it means nothing if he was stood on his own all game protecting no-one.
Each hero has a role, and each role has a simple objective. These are what you should be focusing on, provided you're doing you're objective you're playing fine, any medals are an added bonus. A few examples are as a flanker you need to be taking out the healers / sniper. As a Widow or S76 you must be killing Pharah the second she enters the fight, as Pharah make sure you're keeping the turrets down if they have a Toj or Bastion.
If you achieve your objective you've made the fight a whole lot easier for your team and you're now able to help them with their objectives. Medals are good for XP, that's about it.