A slight blur with a radius of 1 or 2 is usually enough. You can also blur the calculated normal map image afterwards using other tools like Gimp. The normal map calculation gives really bad results without this blurring. The 'Blur'-node (the red one, I guess it's red because it's making the calculation sometimes super slow) is used to make the transition between the stone tiles and the gap between them softer. Such an effect is weird to use to create textures as a bump or normal map should be dynamically rendered in the game (if you use normal mapping) using the textures and should not be prerendered into the textures. The shipped examples are often using the 'FilterEmboss'-Node which is simulating light fall on the material, which seems to be similar to the 'Bump Map'-filter in GIMP (Filters->Map->Bump Map). This example is based on the cobblestone sample shipped with NeoTextureEdit, but improved: Which node is used int the preview for which kind of mapping is shown by the blue D, N, S or H at the right side of the node (see second screenshot below). Urho3D doesn'T come with a parallax mapping shader, so you may want to disable the parallax mapping feature by setting the 'POM Strength' to 0. The OpenGL preview area in the lower left can preview diffuse, normal, specular and parallax mapping. You can move the node view with the middle mouse button and create new nodes with the right click menu.

Gimp seamless wood texture