I just stumbled upon the Massachusetts house while following the trail for the railroad quest. I don't think the house is part of the quest, but I didn't know that then. The house seemed easy enough with a few ghouls, but then I hit a Mirelurk legend and just about pooped my pants. The thing killed my three times before I figured out how to sneak and frag the biatch. I thought that was it for tough foes, but I was oh so wrong. I hit another one in a basemant room with a small pool. I couldn't seak away form that one, but stood on a overlook and fragged the beast into submission. I jumped down and an MFing Mirelurk Queen popped out of that small pool and beat the living crap out of me over and over again. I couldn't run away because the damn thing was between me and my only egress. And having used most of my frags, I was oh so Fk'd. After sinking most of my ammo, stimpaks, radaway (the damn thing shoots radioactive goo from distance) and about 10 lives, I finally killed the thing.
JC, that was the hardest battle I've seen in a Beth game ever! And I hadn't a clue.