There’s a lot of other curses and ways to apply them …
One of the easiest ways to ensure your enemies are always cursed is to get the Doom Bringer node in the Transplant skill tree. That node casts Bone Curse upon arrival with Transplant, which means every time you use your teleport (transplant), you curse enemies in an AOE.
You can even activate the node Signet of Agony in the Bone Curse skill tree and turn it into an aura.
Try some curses besides spirit plague. The following build guide focuses on Harvest, and using 2 AOE curses. It’s fun.