Well, I'd think it makes sense to adopt the ritual to the sacrifice. Werewolf? Better do the ritual during a full moon. For the Focused Practitioner you could do the ritual close to something related to the focus.
Basically, the ritual would then allow the properties of the sacrifice be distilled in its purest form, so the sorcerer can digest them. Of course, that could have side effects similar to summoning a demon, but kind of subvert the trope. If he sacrifices an aeromancer on a stormy cliff, the wind itself might howl in protest and come after him. Siphoning the werewolf out of the sacrifice might also siphon the human out of him and go into the nearest animal, creating a wolf-were with the memory of what happened to him.
The players could stumble upon those first. The wind spirit is wreaking havoc over the city, and the players need to find out why. The wolf-were is confused and kills people at random, and the players need to find a way to make him stop. The more of these side-effects you've got the players figuring out, the closer they will get to finding the sorcerer and putting an end to his plan.