well, if the issue is with modeling, the screen you've posted shows lack of polygons to define shapes and volumes. Additionally, you need detail map, normal map ( and specular and so on with a good shader ), lightmap ( with a good light setup ) and variations ( like decals ) to bring an interesting atmosphere and to obtain…
I'm struggling with terrain too atm. i think you lack of resolution, on your mesh, and on your textures. The splatting mask is really blurry. I wonder btw, if some engines don't do some noise on splatting textures on the fly, to add precision. Also use decals to add some variety. I think u could play a bit with sandbox2 or…