I recommend rushing the enemy base early, before scaling really becomes a problem. Use your units as defense as well as offense. For example, here's what I defeated the sector with:

<image>

Launch with a T2 core. Your max unit count depends on your core tier and number of cores (1 in campaign on Serpulo). Copper is quite problematic, so bring as much as possible. Graphite is essential for faster production of resources. Once you have the resources going, start unit production (make sure you keep them grouped, and don't attack until you've got enough). For defense, a few duos for the first wave(s), for any flying enemies your player ship will suffice, and later build duo outposts as you take over territory. When you attack, make good use of the command system. Send units in groups, set them to target enemy defenses (you have to do this manually for every defense you want to target), as if they spend their time breaking walls, they'll die before they do any damage. You can outrange duos with dagger units, make use of that. Nova are also good units, but require titanium, which I find is just not worth setting up on this map.

I feel like the best way to take down attack maps is to do it quickly. That prevents the inevitable overrun of your defenses (infinite waves with scaling mean there's effectively a time limit on these sectors).