Your job as a concealment operative, solo, in huttball, is to assist your team in controlling the midfield. Lurk, kill respawns, kill solo grabbers, kill catwalk campers. If your entire team is on their side of the map, you're doing it right.
If you are on the defensive, don't kill the enemy carrier- your team will be focused on him. Kill all of his support. Go to the back of the pack and work your way forward. Every person who turns to deal with you suddenly isn't assisting their carrier.
If you're the sole defender in position to defend a cap, hold stealth and faceplant the carrier in the fire hazard.
You're a flanker class, so flank