AFAICT, app-text/docbook2X is here quite a bit like gtk-doc-am for gnome packages - that is not really needed, unless you're doing something odd (like i.e. eautoreconf). At very least, it should be put behind doc useflag - a release tarball already carries the docs generated by that package, so it's only needed if rebuild of docs is requested explicitly.
It is used to build the documentation included in the tarball, but shouldn't be needed, if all went as planned, to build/install from the tarball at all.
Right. Like you said this is not needed. It is probably a leftover from the snapshot ebuilds. I will have a look and remove it
The said dependency has been removed
