U can't use the copied skill in the same turn u cast this card (like any other creature), u can't copy passive skills like voodoo/vampire etc.
So do you mean that you can only copy skills with an active ability cost? Because Vampire is not a Passive skill, it's Active (or if not Active, it's at least Innate).
didn't know that vampire was "active", i always thinked that any skill without cost (0 is a cost, see sof), was supposed to be passive
also, i choose to target only active abilities because targetting devourers/scarabs can be problematic, with their "double" ability