I had to go WAY back to a prior save yesterday to replay the Road to Freedom because I killed the Railroad faction leaders and found out they have good quests and upgrades.
So there I was thinking it wouldn't take long, despite losing almost half of my 56 hrs of play, because I knew what to expect and how to play it.
Then I stumbled upon Mirelurker Kings trying to shortcut across some water to get to a quest. They were a LOT nastier than I anticipated, so I ended up taking the long way around.
Even after finishing the quest, I gave up trying to kill one from very far away atop a railroad car using my 77 damage .308 sniper rifle. Even from that distance he shot rad waves at me, but didn't advance. I'm guessing he either didn't see me, or needs to stay near water.
The weird thing is, that family I did the quest for is the only one I recall having two kids and one parent, yet they live in one of the most dangerous places in the commonwealth, and the kids only complain about being bored. LOL
So Mirelurker Kings are my new for now nemesis, which I need to figure out how to kill. Oddly enough, the save I had to go back to to get to the point prior to killing the railroad faction was the one at the start of taking back the castle. This time killing the Mirelurker Queen was WAY easier and quicker. That was partly why I tried killing the Mirelurker King, even though there were two of them on my first attempt.