How the heck do you guys make a terrain scene?

I tried with Blender and Armorpaint. Armorpaint scales the textures only up to 5. Once you exported it you cannot change the scale in Blender anymore, because everything is baked in one texture. It looks OK in Blender and from afar. But i always make RT walkthroughs like in a shooter game. And at a closer look its plainly disgusting. Tell me how to make it better, please. See example on Github. It is what its called:
You will also need the textures:
Or just copy the repository as a zip file.