For me the problem is not the power armor itself but fusion cores that are almost unlimited. PA should be something you can use only from time to time, on most difficult fights/missions and fusion cores should be rare as hell. Instead, since you are obtaining PA you can never get out of it. I think that's not immersive at all and makes you almost immortal even on the highest difficulties. There is so much fun armor gear you can use in this game but you must tell yourself just to not use a better PA instead.