If this is a one-way system as suggested by all of the diagrams, a fail-safe bias would only be needed on lines where the driver might be disabled. I would normally expect this only on the backbone.

Since you say in your original post that you're using CAT-5, I certainly hope that you've chosen a pair, and not two wires at random ;-)

I wrote If the supplies are floating you should connect a common. If the display power supplies are already earthed, then you already have a common (of dubious quality).

The "Ten Ways..." app note has some alternative suggestions for receivers, which might do a better job of noise rejection. Do you have the liberty to try these?