Step one: Hide

Yep hide, don't make yourself a target and wait to find a target. Now you have a small window of opportunity.

Step two: Maximize damage in your up time (the time you are alive).

Throw sticky, plasma, mortar volly, grav, grav, HIB, Demo (target usually dies here and you have done some nice AE on his friends), FA (if target is still alive they will more than likely die here). Now you have done a great deal of damage without having to expose yourself to many of the enemy.

Step three: Run for your life.

At this point the melee will see what you have done to their team member and make it a priority to execute you for war crimes. This is where it becomes a fight for your life and you have to depend on your team to help out. Pop your shield and run/los/kite them away from the area and hope you have solid team members to peel and pick up. Use your insta/big heal to keep you above that dispatch range...once you hit that 30% mark its usually game over man. The better you get at survival in this phase the more time your team has to win the encounter and help you stay alive.

Step four: Respawn (if you die) or rinse repeat (if you live).

Try and target the softies...a smash jug is a better target than a sentinel until the sent has blown his cooldowns. Drop your stealth scan just before those stealthers will use their escapes...nothing pisses them off more than wasting that long cooldown escape. After a few of these moments of hellfire expect to start having stealthers hunting you for a trophy.

Just don't forget that with your heavy armor and huge weapon the most important thing to do is hide and let a team mate eat the facesmash.