Umm, that heightmap 0/1 thing is because the height maps are a .tiff file, and yep that is an issue oddly the landscape meshs all slot together quiet well as long as one has the patience to line up a vertex to another on the overlapping mesh.
Keeping mind I didnt mention the size of the landscape mesh or the height map for that matter if your apply todays standards I could forsee something getting over loaded.
I am not at my PC at the moment so can’t give exact sizes of the height map files but from memory 389x389 is the minimal, and maximum 800x800 ish.
As you can imagine from those numbers the height maps or the data im working with is VERY old as in 2001 old, about the time Guild Wars was first released.