I’m disappointed if it won’t flatten a building, it does on the simulator, but I’m still glad it ruins their day! In my version, it is guided by the pilot’s lock on throughout its flight, it goes up, acquires the target and comes straight down.
The hellfire has a pretty parabolic trajectory, so it sounds right. Although the newer ones have a flatter path.
The old ones were laser riders, the new ones are fire and forget.
Blowing up a building(depending on what you mean by building) is pretty serious stuff. It takes a big weapon to do that. Kill everybody inside takes much less.