Please consider install Noto CJK (Source Han Sans) font family which provides seven font weights and contains most CJK characters in Unicode. The installation will significantly improve the quality of SVG images which include CJK characters. This font family is open source under SIL Open Font License 1.1.
- Debian package: https://packages.debian.org/jessie-backports/fonts-noto-cjk
- Ubuntu package: http://packages.ubuntu.com/trusty-backports/fonts-noto-cjk
- Source (Google): https://github.com/googlei18n/noto-cjk
- Source (Adobe): https://github.com/adobe-fonts/source-han-sans
Also since fonts-noto-cjk is still in backports for both jessie and trusty, I guess you need to add the packages to apt.wikimedia.org also.