I first ran into this building with my high lvl BoS PC. It was not much of a challenge in fully modded out power armor and heavy weapons on VH difficulty. I decided to head there with my stealth PC (lvl 48) who only wears ballistic weave clothing for armor and I had Deacon accompanying me. This PC uses Overseer's Protector and Deliverer, while sneaking these 2 weapons are extremely powerful even without the sneak perks that I have.
Anyways back on point, I went there to get the bobblehead. Even tho I had already been there with another PC and knew what to expect, it turned into quite a fight with my stealth PC. Those gunner's on the roof were tough to take out once my cover was blown. I bet I died 3 times to the one with the Fat Man, and at least once to the one with the missile launcher. I eventually had to dismiss Deacon who kept blowing our cover and take them out very slowly and stealthy.
After playing thru all 4 endings with 4 very different type of PC's, (two who wore PA and two who didn't) this game is much more fun IMO playing without the PA. There just comes a point where you become an invincible tank in PA and especially with heavy weapons, and it makes the game boring. I have continued to play my non PA wearing PC's but haven't touched the other 2 since their respective endings.