This is a very imaginative line of sight question that is clearly contradicted in the rules, but I think it would make more sense anyways.
Suppose a large monster with a ranged attack such as a naga, demon, chaos beast etc wants to attack a hero but LOS is blocked by multiple small monsters (beastmen, skeletons, sorcerers, etc). Since the creature is so much taller than the small creatures, wouldnt he be able to attack the hero anyways since he sees over the heads of the small guys?
<====big guy (demon, dragon, etc)
O
<O>
O
O
/ little guys (beastmen)===> <===hero