the cloner Blend mode blends parameters of objects not the effects of deformers on the object. You just need to put the displacer in a null with the cloner (since it can’t be a child or the cloner will try to add it to the clones) and then set the Displacer Falloff to Linear and set it to the right size and direction to cover the clones.
This example uses R20 with the new separate Linear Field object for falloff but the same thing is possible with R19 and below you just have to move the Displacer deformer to get it where you need it.
