I hesitated to answer because our zones are so different but since no one else has I decided to share my experience.

My potted heuchera is also in a terra cotta pot. I bring it into my unheated garage for the winter. It does not get any water until I see new growth in the spring. But, the soil is frozen all winter which might be different than yours.

Why not do the same with your heuchera as you do your hostas?

In zone 7b, there shouldn't be any significant freeze-thaw cycles - it just doesn't get cold enough to freeze ground soil to any serious depth. Plants grown in containers are a bit different, especially if the containers are small. Because there is no large insulating soil mass around the root system - like there would be for plants grown in the ground - they can be more vulnerable to cold temperatures.

I have no concerns about leaving heucheras (or any other hardy perennials) outdoors in containers over winter, regardless of size of pot. But then I am in a bit of a warmer winter location than you. I would think treating them as you do your hostas, as mnswgal suggests, should be just fine.