Don't know. I don't run xfce, so I don't know what it depends on. Here's how I did it, if you're comfortable with aptitude's interactive resolver:
bash# aptitude -s purge '?name(systemd)?installed' libsystemd0+
then review the list of conflicts and suggestions in simulate mode. (I started without explicitly marking libsystemd0 for install, but after I realised its list of reverse-dependencies, I relented.)
I proceeded by looking at the 800ish packages it suggested removing, picking two or three packages I use and marking them as rejected (in my case, initially kmail, kdm, xserver-xorg-video-all), cycling to the next suggested resolution. then repeat. Whenever it suggested installing a systemd package, I rejected that suggestion too.
Eventually I settled on removing about 20 packages I didn't need (networkmanager, gnome-shell, some evolution packages, etc). Then I re-ran it without the simulate option.
Afterwards, I realised that I really wanted something to manage the network for me, so I had to manually bring the wifi network up, and
bash# aptitude install wicd-gtk wicd-cli