Ding! Thats one of the current rough edges of linux. Do U roll back, drop the package you wanted to make, petition the author of the software to support the newer gstreamer, or switch to pulse & or petition the author to support pulse?.........so many questions.
I have installed xfce4 with success (after intalling gtk3). However when I tried to install xfce4-mixer the installation failed as it has been required gstreamer-plugins-base-0.10 (at least version 0.10.25).
I have tried installing gstreamer, for a beginning, but the output says gstreamer is already installed. thanks. Cezar