I playing last human mission Frostmourne on hard. Destroyed all undead units and buildings. There is only Malganis left, but he is invulnerable and standing still. But mission still not completed. Seems like bug.
I finished the mission couple days ago no problem.
i have the same problem, he is invulnerable, so i did the level all over again, same result, he is invulnerable and there is no way to progress