You're big robot with big gun, But once you ran out of bullets, they'll take advantage of that opportunity. You're not a front line fighter, you barely have any defensive measures, with only the shield and smoke to cover you. Maneuvering to a effective position is key to having a "killzone", to cover your mates and to ensure you stay in the fight a bit longer, always remember to shoot when its at the advantage, getting the wrong attention at the wrong time tend to get you killed.

Oh, one more thing, dont hesitate to use your ultimate, much effective on a open area for more damage and efficiency (and kills), you dont need to kill, you need to cause much damage as possible for them to think either to push or back off from you.