I'm not giving excuse to ED's modeling of damage, but in this instance -- it's realistic. Picture a brick house for instance with concrete foundation... soft soil around the house. Bomb fuse is set for impact, but due to soft soil it digs little bit before explosion. Frag is going outward from our crater. Blast removes windows and some tiles. Maybe creates few nice cracks in the foundation. House still stands...
So to solution. Few B-52s drop all of their load out on a city. What do you expect to happen....
Do they model each brick and kill your computer dead once it tries to simulate those explosions. Do similar to BF3-4 building damage...excellent on localized small map but requires quite a large team. Or do they add few textures to the house with HP. If HP this - then show this texture. No HP - show "dead" building.
Choices... Are you asking to add less "HP" to building so that your expectation of reality is simulated or...