Manually Rooting - What Else Is Needed?
You also need to copy the busybox binary to /system/bin and /system/xbin. This may be the only step you're missing. Also, you only need one of superuser or supersu.

edit I was wrong, although for anyone else following along, the busybox binary from busybox.net includes su, which I thought was pretty cool. Anyway, it seems that rooting a modern android phone takes a bit more work. I took a look at the supersu zip, and from what I can tell, it creates a whole new ext4 system image and mounts it at /su. It also installs a few system daemons and initialization routines.