I'd be a little bit more behind Ivy's design if it looked as though they'd actually followed through with it in the game - In the trailer we got for Ivy, recently, it just looks like she's wearing a cardigan or something. Given her background, why not a lab coat? You can still play the idea of 'revealing and sexy', but then I suppose we'd be deprived of ass-shots.
I'm not a big fan of the pseudo-realism they're seemingly trying to go with in these characters, but I still think all three could've been better interpreted. For instance, the ultimate Scarecrow design for me is still the one they came up with for the New Batman Adventures - as in, less obviously scarecrow-esque, and more just plain scary.