@lilhaselhoffer,
Of those settlements you mentioned, I have all but Egret Tours Marina, and so far they've not been the disaster you've described. I'm also only putting up the lowest level turrets, and never more than 4 in a camp, usually two. It's not hard to predict that missile turrets + Bethesda AI = trouble. And laser turrets take generators, which can require repair at times.
I'm having a lot of fun with just the vanilla version of the game, and I don't plan on leveling too high. I've read some say it starts getting boring at level 45, depends whom you ask I guess. I've been on the Bethesda and Steam forum a lot and every time someone complains about settlements being broken or chaos, others chime in saying they're great, so.
Let me go at this one more time.
Missile turrets provide the greatest defense, for the relatively cheapest investment of rare components. Oil, gears, and everything else is easier to find that fiber optics and nuclear material. Put simply, to build enough heavy laser turrets you'll need to constantly scrounge microscopes, anything with nuclear material, and make sure that you can link together a metric boat load full of generators.
Why do I need turrets? The settlements function on 10+Charisma for their maximum number of settlers. This means settlements need to have 2*(10+Charisma) defense to not be attacked constantly, unless of course you want to make money off of settlements. If you build a water purifier that produces 40 water, that means you've got to increase the defense by that much. The problem there is settlements have a limit on construction, and turrets break down at random.
So let's say you've got just enough Charisma to do supply lines. That means each settlement has 16 people. The defense rating will have to be 56 (16 food, 40 water) to prevent constant raids. Our turrets each provide 4 defense, so that means I have to build 14 turrets. Each turret requires oil and gears, two relatively difficult to find items. Now, each of those turrets randomly breaks down over time. This means that I've got to go out and harvest more oil and gears to repair the turrets, which cripples both my ability to produce more of them and my ability to build more stuff at the settlement in question. I haven't mentioned it until now, but those pesky build limits mean a place like hangman's alley could reach "full" status before you can build enough turrets to protect it (without using the ability to break things down to decrease the amount of items the game says are there).
So now we have a crappy design choice question. Bethesda has designed the turrets to randomly fail, they've placed a cap on settlement buildings, and they've made the truly powerful defensive options an issue. Do you try and have fun with the settlements, and make some money to make up for the resources they consume in insane quantities? Do you forego settlements, because they're a micromanagement nightmare? Do you install mods to fix all of this broken mess, and use in game "cheats" to make the building reasonable (read: modifying crafting limits by breaking down items manually)?
Here's my truth, Bethesda decided to throw the kitchen sink at this game. Crafting is popular, so they put that into both the guns and the settlements. Fallout 3 had a successful mod that allowed you to build your own home, and so did Skyrim, so Fallout 4 "expanded" upon that by having more potential homes. People like the idea of leveling up, but hate numbers, so the level up system is now based upon perks, that sometimes need to be chosen at certain levels because it's the only way to match the power-up of the enemies that a level increase causes. Bethesda wrote themselves into a corner with the ending of Fallout 3, so this time they wrote an ending that feels hollow so that no matter what choices are made you can walk back into the world and keep grinding.
I'm sorry, but where's the logic? Where's the reason to replay this game a second and third time to be somebody new? In Fallout 3 you could be someone, though it largely came down to good or evil. In New Vegas I could replay that multiple times, and get a new ending each time that felt like my choices mattered, and that I wasn't stuck playing what the developers thought I should be. In Fallout 4 I murder the people I don't like, but the choice is largely which brand of jerk I am. Do I murder the people trying to learn from humanity's mistakes and give us a new future, by kidnapping people in the night? Do I murder the people trying to free what are functionally slaves? Do I murder the people who don't care about the daily lives of the people, just as long as they've got technological superiority? I'm sorry, but after the second ending I felt hollow. I wanted for someone to write a mod, and put the long mile into 4. I'd happily set those nukes to hit the brotherhood and the institute, and that's largely my happy ending.
I've never felt so hollow at the end of an RPG. There was no role to play here. There was the great question of which sociopath I was, and how much niggling crap I was willing to do to level up. Bethesda has produced one of the poorest entries in the Fallout series with 4. Yes, it's more stable. Yes, it includes a lot more contents. The problem is that it's poorly balanced and thought out content, that works to highlight the failures rather than gloss over them. It took me until level 60 to see all of these flaws, because up until then the progression hid the mechanical flaws. When it takes two days of play, and a body count higher that WWII, to level up the progression no longer exists, and it's no longer possible to hide the flaws.
I'm telling you to finish the game before level 60 so you don't see behind the curtain. If you want to ignore that warning, I can't stop you. All I can do is tell you my opinion would be different if I'd stopped there. As it stands now, I can't help but feel that Fallout 4 is technically better than 3 and New Vegas, yet hasn't enough soul to truly be comparable. Maybe the DLC will fix that, but what I'm actually hoping for is another Obsidian joint, that allows us to have the heart of New Vegas, the quirkiness of Fallout 3, but the improvements and stability of Fallout 4. I likely won't get it, but I can dream.