While it can be used to make enemy weapon users ineffective, this skill truly shines when used in skill combinations. The following are some suggestions:
As a primer for Virulence. Because Virulence is in a different attribute line (Death Magic), you can simply cast Enfeeble at Curses rank 0. Virulence will re-apply the weakness condition for a longer duration.
As a primer for Stoning, which knocks down weakened foes.