Well,with a standard load I don't think .45-70 will do that much damage to a deer,it's actually a good deer round,now if you mean a .45-70 loaded to max pressure to match the .450 Marlin ballistics than yes,the .45-70 might be a little bit much.
I live in Ohio. So for Deer its bow and Muzzle Loader. But I hunt in WY as well. I choose .270 and I am going to lhndload 110gr VMAX for Varmit ant 150gr for Hogs her and any large game out west. That covers me home and away.