Hitler's death in World War I would essentially butterfly the NSDAP's rise to power. Another figure would simply not have had the oratorical talent or the ability to attract the organizers necessary to build a formidable apparatus for the party, and - very importantly - might not have had the ability to present himself to German "traditional" right-wing circles as the only figure with the popular support needed to bridge the power vacuum in the Weimar Republic and restore Germany for what it once was; and that's not even mentioning whether a similar figure would have been able to subsequently destroy the power of the traditional Right and consolidate complete power over Germany.
The likely alternative to Hitler is a military dictatorship - one similar to the wartime one, and led by traditional right-wing figures. This was the path the WR was going in with or without Hitler; the state was far from a liberal democracy (I mean, Hitler's "trial" after attempting to overthrow the government in 1923 tells quite a bit about the Weimar Republic's political system). I am doubtful whether someone else would have pursued German expansionism over Europe so aggressively, though I think it is more than likely that this new state would focus quite a bit on recovering German territory in Poland and perhaps annexing Austria. A Holocaust is less likely without the Nazis' racial theories, but the traditional Right of Germany had a far from positive view of Jews (see, for instance, the 1916 census designed to blame Jews for being "disloyal.")