In our case depends on the scale of the battle. For example, If a hut represent a village and a unit represent a whole regiment, then a simple hut model blocks the line of sight. If the scale is minor, and a hut model represent only a structure and a unit is bunch of mens then it doesnt block the line of sight from a high level.
These details are talked between players before the game, scenery by scenery.
Thats the way we do,
cheers