Helldivers Objective - Activate and Defend Launchpad (Bugs)
3With Bugs, your two main threats to the objective are if Behemoths spawn too close or Impalers spawn off screen and start sprouting tentacles that can destroy the objective very quickly. Both scenarios are best avoided by not standing too close to the objective so that tentacles / Behemoths that spawn near you are a little further from the objective.
The Brood Commanders and other enemies aren't really threats because you can tag them with fire and they will chase you rather than go after objective.
Outside of that, the main goal during any defend objective is to prevent alarms, and if alarmed don't lose sight of the objective and use slow / stun / kill to keep enemies from reaching and hurting the objective. I personally think using Slow / Stun is better / safer choice than AT heavy kill options which also put team / objective at higher risk.
The most important thing is really how the team forms around the rocket and covers their own sides for most part, and get help only as needed and promptly return to covering their sides.
The Bugs are most susceptible to being distracted by the NUX-223 Hellbomb so if there are any Destroy Bug Nests objectives on the map, each player can be throwing one of these in the direction they are covering to keep Mantis and Scouts pre-occupied.
This video contains 3 Activate and Defend Launchpad objective completions that I feel demonstrate the guidance I have shared above.
Note: If you leave the area while countdown is still active, you will automatically fail the objective.