I would suggest starting a whole new material and assigning the instance to the landscape.
Then, create the “layer” nodes without the node you call “magic”.(Type in landscape, it should give you a one pin entry that you can rename to match the layer name).
At first, since your layers on the landscape are already painted, you can try just using the Layer as the alpha mask of a Lerp and plug the lerp directly in the base color output.
This should effectively color the landscape in black and white depending on the weight paint of the layer you picked.
You can say daisy chain the lerps (out pin goes to A, color pin goes to B) to get the rest of the layers to paint on screen.
This gives you an idea of how to play with the masks and what the layers do.
Now that you know, you simply replace the lerp with a layer blend and blend materials instead of a single color, change the output to a material node and plug the last blend in.
I’m absolutely unsure why, doing this cost less then the layer blend node. I have red several Epic employees here in the forums stating it should never be so since the 2 processes essentially do the same exact thing.
However, this was the same for me in 4.22 as it is in 4.23, I dont believe it to be a bug, I just believe that the math to add/remove layers in the blend layers node is what takes more time.
I need to go and see what the code for the node actually does, but technically it should subtract the layers from one another before blending.
With my way, this isn’t being done unless you do it explicitly for every single layer. The result being that the material renders out faster (but ends up Maybe costing more if you layer 10 layers together instead of just a few, within the same tile).
Hope that makes sense. I’ll be reviewing the shader code later on as I’m interested in understanding exactly what or why this is happening.
My alternate solution is to limit the landscape mat to just 1 output of layer blends. I used to have a few sets to deal with tessellation and normals, I’m willing to bet that was the original extra overhead I was fighting against.