Configure scripts don't recognize the libxml2 version properly. I tried the pkg-config command manually that configure uses. It works just fine. pkg-config yields the correct responses. I don't know why the configure script fails. I wanted to attach additional files for reproducing and tracing the issue but there's no attach function unfortunately and the comment became to long...
Created attachment 94050 [details] emerge --info
Created attachment 94051 [details] what emerge dbus yields
Created attachment 94052 [details] the config log to the emerge dbus
Re-test with dbus-0.62-r1 please. Reopen asneeded.