Jacob is useless

I actually thought the exact opposite. Jacob was useless before, a muggle roaming around the wizard world, while a fricking Wizard-Hitler moves around who likes muggles as much as Hitler the jews. I never understood why he survived the first two (and the faceoff in the final, but the newly pure hearthed leader can't directly do open "Avada Kedavra"). But beside this, he had finally a purpose. Using a muggle who seems to earned somehow magic power must be the worst nightmare for Grindelwald and his Nazis, so perfect to distract them. Much better use of him as one and formost two, where he was awfully used.