This thread may be a bit of age but...
Helped me to fix size of fonts which were way too big with Xorg, but besides from gtk2 apps also jwm (only dependent on X libs) and opera (in X toolkit mode) were affected, while with Xvesa font sizes have always been perfect out of the box.
Using "xrandr --dpi 75" fixes font sizes, though I lost a lot of energy and time, not realizing that with "jwm -restart" the new setting wasn't applied - it needed a kill and run cycle.