This has been mentioned a few times on the Wayland IRC, so I feel it's apropriate to open a bug report for this.
Currently, In order to use Xwayland, you either need a slightly modified ddx for your video card, or to use the wlshm "driver"
However what probably would be better for xwayland is a fake ddx similar to wlshm, ( most likely using egl?), so that xwayland can be hardware accelerated, without maintaining X drivers, or requiring the xwayland server to run as root.
Axel did this: https://github.com/axeldavy/xf86-video-wlglamor.git