Hello! Sorry I am late to this thread! It's funny, because you described yourself and you are EXACTLY my coloring, height, and body shape! I am about a size smaller than you now, but I've been hardcore dieting since January and I *just* moved out of the 14s.
I too have been on a dress hunt, for work and for play, and it can be discouraging. I have had a lot of luck with Ann Taylor Loft and Ann Taylor Factory Outlet, and I was recently very pleasantly surprised at how many suitable dresses I found at our low-rent horrible Macys. (If you haven't been in yours in a while, wander through just to see. You might be surprised too!) Try Nordstroms as well when you are in the city.
Most of what I have found so far has been black, but there's such variety in them I've been okay with that. Here are some photos and/or links:
Alfani at Macys: http://www1.macys.com/catalog/.....x-xx.index
On me (under a cardigan for work): http://www.flickr.com/photos/k.....552470668/
ATL lantern sleeve dress: http://www.anntaylorloft.com/c.....ory=Misses
(I haven't posted any photos of it yet, but it is FAB. I was thinking about wearin it today!)
AT Loft polka-dot dress (this sold out within a week, sorry. But there are lots of polka-dots out there still): http://www.flickr.com/photos/k.....683817607/
AT Factory brown a-line with white bottom. I ended up returning this because I got smaller than the size, but it was still available at ATF when I went there last weekend. I loved the structured feel of it!
http://www.flickr.com/photos/k.....683817607/
ATF blue-and-black patterned knit dress. This is going to be my go-to dress of the summer. I love everything about it. Also still available at ATF.
http://www.flickr.com/photos/k.....203863601/
Banana Republic also has a number of their dresses on sale right now, and you can get your size online from them. I do a lot of ordering and returning with all stores; don't be afraid to try! You can always return it.