Is this a case where a figure doesn't have LOS to an enemy because another figure it doesn't have LOS to is in the way?
I believe that your interpretation of the rules is correct, since they do seem to be pretty clear on that point; here's the "Line of Sight" section from the Rules Reference Guide, page 16:


  To determine line of sight, the player draws two imaginary, nonintersecting lines from one corner of the attacking figure’s space
  to two adjacent corners of the target’s space. If either of these lines
  passes through a wall, figure, or blocking terrain, then the figure
  does not have line of sight to the target.


(I've added the emphasis on "figure", the other is in the original.)

The way I'd justify this slight oddness to myself is that when you're targetting a figure, it's one particular figure that you're trying to target - there's no way to say, "this would probably hit one of these two rebels", and if there were that'd have to take into account their different distances, etc. It'd be a much more confusing combat system if that possibility were taken into account. So I guess it's a nice simplification to say that you're just targetting one figure, and anything that might get in the way blocks that intention, even if it's another hostile figure rather than blocking terrain.