Shipyard as security.
For the first part, as an engineer, rush to the main barricade and place a turret just in the entrance, it should keep the enemy at bay for some time and allow your team to have an advantage. Plus, always buff your teammates. If you can buff them with kevlar too, that’s a nice bonus for them. Keep the enemy at bay during the first wave.
If you don’t succeed quickly in securing the area, you will have the enemy team building the main barricade. Move up just a little so that you can pick off the engineers building the barricade while only exposing your head. Then move in carefully, pick off the straglers, build your turret and move onto the crane to do the objective.
The key is :
-Buff your teammates
-Prevent the enemy team from building the main barricade or any barricade at the beginning and during the entire lengh of the game.
-Secure the area around the crane
-When you’re working on the crane, if there are a lot of enemies coming, stop and kill them first
If you don’t risk being overrun at the crane, you can also stop in the first command post to upgrade it to give an health bonus, if you have the ability. It helps too.
It takes some work but once you found the right tactic, the mission isn’t really that hard.
Same goes for the second part. Secure the area with a turret and a mine, keep the enemy at bay. Once you’ll have cleared it well enough, bots will start hacking it.
I finished the mission on normal. It’s really challenging. During the first part, I almost banged my head against the wall in frustration. But once you start to come up with a tactic and know what to do, it becomes easier.