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.
In combination with Fevered Dreams to weaken all foes in the area. This is superior to Enfeebling Blood, which only weakens foes nearby to the target and has a health sacrifice at the expense of using an elite skill.