Personally, I like that the game skews a bit in the favor of offense.
It keeps combat nice, short and sweet. If you want combat to be longer
there's nothing wrong with that, but that's what basically any rule
change that helps defenders does. Using the rules directly from the
book my games have had combat that has had a very high level of
tension because any given attack could end a character's life (or at
least deplete their Willpower).
From a realism point of view, while it is actually harder to shoot
someone's moving legs than their head, it's not easier to get your
torso out of the way, so you're not wrong that it's not necessarily a
perfect model of realism. My opinion is that there's nothing wrong
with that. I think the game is made better by having the hardest thing
to hit or defend be the head, or the four critical boxes, if you want
to think of them like that. (Incidentally, the reason that I regard
those boxes as head boxes is that if I start thinking of them as
"organ boxes" it stops making sense that a helmet protects, for
example, your kidneys. My own sense of realism seeps in there, I
guess.)