I would say that of course the results are going to be different, it isn't CMx1.
CMx2 has new mechanics and behaviors all over the place, so things you expected to work in a particular way won't and it will bite you.
And, as always comes up, the casualty rates are reflective more of the person in command. If you had low casualty rates in CMx1 and you and your opponent would quit/surrender/ceasefire when they got too high, then you can still do that in CMx2. On the other hand, if you had low casualty rates in CMx1 and your opponent had huge casualties, then you were just far outplaying them - not really keeping "realistic" (or maybe historically normal) rates.