I agree that the dresses are not too short for you. Actually, the length suits you well. You have both the body build, and the legs, like so many have said, for that length of dress. Be proud that you can rock them so well :-).
I don't think they are too short for the workplace, wither.
All of the outfits look great on you. Your #4 outfit seems to make my point; even though it is still above the knees, it looks really long on you. Not in a bad way, though. I like how the skirt transitions the black top into the white shoes.
I agree with Donna's comments.
The #2 dress is a high activity look, so tennis shoes seem appropriate for that dress. It's actually a great look if you plan to do a lot of walking.
I am partial, though, to #1 and #3. Both actually work so well with your hair. #1 gives continuity, while #3 gives a complementary contrast. Those sandals seem to be a neutral that can work with almost anything. The metallic sheen draws my attention to your lower half, giving them their rightful attention in the looks.
I agree with Susie that your hair is very pretty. I'd actually like to see it a little longer. I think longer hair will work well on you. Not every woman can rock it, so take advantage of that ::-).