Building mozilla-1.7.13 with all optional components disabled including "moznoxft" (no xft) results in a mozilla-bin that does not work: /usr/lib/mozilla/mozilla-bin: symbol lookup error: /usr/lib/mozilla/components/libgfx_gtk.so: undefined symbol: pango_x_font_map_for_display Building with all optional components disabled but with xft enabled allows mozilla to work. I haven't tested whether "moznoxft" is simply broken or is only broken if other optional components are disabled.
Mozilla will be removed from portage. In fact, it should have been gone long time ago. Dead upstream, unresolved security issues. See Bug 135257.