Hey,
I didn't find any mentioning of this neither in the rules, FAQ or forums, so I'll ask then:
Does a hero have a line of sight to a large monster if the hero would be able to trace a straight line to one of the spaces occupied by the monster if an other space whose centre the hero doesn't see and which is occupied by the same monster didn't block the hero's line of sight? In other words, can a space occupied by a large monster be ignored when tracing line of sight to the same monster?
We've played so that the space blocks the line of sight for both the hero and the monster as we can't find any rule to be against that. Although in my opinion it's quite illogical that a hero can't attack a monster because the monster itself blocks the hero's line of sight. The monster also prevents itself from attacking as another space occupied by it blocks the line of sight.
Hopefully someone understands what I mean...
Tseitsei