is it possible to create a Weakaura, when one is the nearest target of the Unstable Voidfiend and he is going to Voidstep on you?
As I said, I don't know if it's possible to create.
I'll double check on farm tonight but I don't think they cast at you/target who they are jumping to or anything which would make it impossible to know who they are jumping on (and thus where).