Quoting "Osamu Aoki" <osamu@debian.org>:
XMLROFF may not stop build but that does not mean they build usable page for CJK (i.e., zh). That was the reason I am using DBLATEX (DocBook XML to Latex using XeTeX backend) for DDP projects.
In fact, the Makefile for the refcard choses between dblatex and xmlroff on a per-language base. In general, dblatex gives nicer output, but in some cases xmlroff works better. Try to play with the switches in Makefile and compare the results...