He was? I honestly didn't notice. That is not beyond the general slimming and streamlining most of the male characters were treated to. One of the major flaws of BAT, I'm always though is how all the men seam to have such huge hips. While some of the women admittedly looked a little too pixie like, in an odd way I think it suited Barbara at least. There's something about the old design that made her look a little to young for me, though that might have as much to do with the original voice actress too.
As for the Riddler, I think he's an almost impossible character to write for. Nobody can ever seam to decide if he's a vanilla Joker of a campy Luthor. Personally I've always thought he should be played as something closer to The Question (and not just because of the ? fixation.) That is a fierce intelligence but misunderstood and a notch or two past that old genius/madness line.
As for Oswald, it wasn't just his character design. I liked that they made him a semi-legit businessman, somewhat filling the void left by all the old mob bosses. A more stable presence that Batman can intentionally keep in place to block anyone more dangerous muscling in.