old long fellows island gets hit A LOT. They only spawn in the direction of the cabin's entrance though. So feel free to just set up a big missile launcher assembly around there and surround your small town with those metal spikey palisades frm the nukaworld dlc. Job done.
I like all the concrete walls used as fortress elements. They really are the best "fence" in the game, in terms of ease of use. The little skinny pieces make anything possible.
I armored my fog condensers with the 4-foot sections of concrete wall, built into a tiny vertical tube, then a second section atop, protects them completely. Haven't lost one yet. I've also been experimenting with building below the ground image by sinking a workbench backwards into the rock face (got the idea from Fallout Gaming Shelter's channel). So, I've built a generator and two missile turrets behind the rock face towards where your attack occurred. I'm thinking that the missiles will fire outward, but cannot be destroyed by incoming attacks, like my surface turrets. Once I armored the fog condensers, I attached small floor pieces to two sides, added turrets, and then connected them with wall section, creating my defensive line. Of course, I haven't been attacked since I've built the experimental sub-terrainean turret defense system (or STD's for short! LOL).
I never get attacked like that after I do the quest about the raiders. But, can I say, That settlement build... Wow doesn't exactly say it, I'm gona go look for more now.
Critical banker. The gameplay is easy; it doesn't matter what your build is. If you build settlements, your xp from it puts you up over level 100, where nothing can even hurt you.