Draw calls are definitely one of the biggest bottlenecks in OpenMW's rendering right now. Morrowind is full of tiny meshes and has lots of them as it's from an era when draw calls were never as much of a bottleneck as drawing more polygons, so splitting them up into small groups to be able to cull as many as possible was a good idea. The linked DOOM 2016 frame analysis says it's doing about a fifteenth as many draw calls per frame as we are, and that's definitely for a much more complicated scene.Also, draw calls really aren't an issue in any of the games OpenMW targets.
We're hoping to implement some kind of batching system to combine multiple meshes into one draw call, and that should put a big dent in the number of draw calls.