Troubleshooting:Xorg
If your X11 server is not working, check the syslog with logread and the /var/log/Xorg.0.log files via SSH for helpful messages.
X11 segfault
Example output from running XFCE4:
(xfwm4:2538): xfwm4-WARNING **: Cannot find visual format on screen 0 (EE) Segmentation fault at address 0x4 (EE) Fatal server error: (EE) Caught signal 11 (Segmentation fault). Server aborting
This might get fixed with this patch (see #779).
Strange refresh rate
Android devices seem to usually have a refresh rate of 60 Hz. If you have a very high or low refresh rate, that does not make any sense, try the patch from !348. If that also fails, try to add a X11 modeline with the correct refresh rate.
Output isn't displayed right for other reasons
Try the patches from Troubleshooting:display.
Is TWRP working?
Try to compare its framebuffer output code with xf86-video-fbdev. If you go down this road, please expand this idea with more information.
Use Xweston instead
If Weston is working, but X11 is not, you could try Xweston to simply run your X11 desktop completely inside Weston. Currently, that is only an idea with implementation work beginning in !909.