The way I have been playing I have been having a unit of 3 models, 2 standing outside of area terrain and 1 inside of area terrain. Assuming nobody focus fires on the unit I assumed that they would get the cover save due to at least 25% of the unit being in cover.
However, I have been trying to find anything that supports this in the rule book but I could not find anything for sure.
Does anybody know where in the book it would support or deny the ability to do this? (Including if the closest model to the shooter is outside of cover)
Again assuming no focus firing