In UDK (the image I posted above) it’s a right to left setup. In UE4 you should go from left to right so your wires look much better.
Instead of using TexCoords use LandscapeLayerCoord.
You should also use a LandscapeLayerCoord for the splat map itself. (Plug it into the UV input of the splat map). For this LandscapeLayerCoord node (only the one that’s plugged to the splat map) you should enter a value equal to the terrain size. For example if the terrain is 4033x4033, you enter 4033 for LandscapeLayerCoord.
Once you did this, apply the material to the landscape and it should be working as expected.