Looks to me like the pickup is pooched. Volume should be even all the way through the length of it. If you replace it and still have hot spots you can put a slice of masking tape on the quieter string sections on the bottom of the saddle. it provides better contact with the pickup and can even out the volume. You might have to add two or three slices at different spots on the saddle. Kind of a cheesy repair but it does work.
