Rwos: He could still damage history, perhaps beyond our ability to fix it. And he didn't fail at Asgard - he left before doing anything. The Darkstar had to have warned him and convinced him that killing Deac Starkiller would alter this. And since Deac is no longer under the protection we are, it could work!
Forum A-Wing pilot of mysterious and indistinct gender. Aresener now and forever.