Yes, Hitlers policies resulted in bad things happening to a lot of people he was most definitely a bad guy. But his original motivations and the people he worked with even in the middle of the war paint him as a lot more unstable leader then he initially appears and his intentions vs the results seem to match up with that. I, personally, think Stalin and his regime and the atrocities it committed was a lot worse and not simply due to the body count being so much worse.
But my only point to that is that I think Garrosh is a better parallel to Gengis as a result. Gengis was able to create alliances with the other tribes which was a large reason for his military power and success, but he also had a lot of issues with his alliances at the same time. This is pretty much Garrosh, accept Gengis was much better at it then Garrosh.