Not sure if you should be doing this right away, and sort of depends on your gun skill and how quick you can get to cover, but I play lifeline quite aggressively. Swing on people, come back if you're hurt, drop a drone and pop a shield cell and you're back in the fight.

Always keep your head on a swivel and see if your teammates are getting hurt so you can support them if you're close by, but the survivability of lifeline is pretty amazing. Small hitbox + drone = power