I'm not sure why re-sizing with actor did not work, but then again I have never seen a class sprite re-sized with actor before other than monster sprites.
The only other option you have is to edit the sprite itself. Extract all the images in to a folder, re-size all images to your liking, save and re-build the sprite.
However, doing this will change the positioning in the act, so you will also have to re-touch the act using actor to place the correct positions.