But if ths is the case - especially if images are overlapping - then why can't I just carve through them and hit the caster? I mean, they're just figments - they don't actually block my sword! (snip)
True but you cannot attack the entire space a creature occupies with your sword. A 5' square (or cube, depending on how you look at it) has a lot of dead air that your sword will swing through on a normal miss, forgetting the whole mirror image issue.