I agree it would be good to have the option to turn off things like this for greater immersion, but I don't think it should be tied to preset difficulty levels. Someone may want easier combat but not want to see the dice rolls, or they may want to see the dice rolls but want more difficult combat. Players shouldn't be locked into options that don't impact difficulty.
Instead, they could have gameplay/difficulty presets that can be further customized. That way people can pick a preset if they don't want to manage the settings, but it would allow advanced customizations for those who do want it. It would be similar to how graphics settings are often managed with presets (low, medium, high, ultra) or a customization option.
I also agree a log of rolls would be helpful. I love checking out how it all works behind the scenes.